Burke_et_al-NIL_Reference_Manual_0286-1984

NIL Reference Manual
corresponding to
Release 0.286
January 1984
Glenn S. Burke
George J. Carrette
Christopher R. Eliot
This report describes ongoing research at the Laboratory for Computer Science of the
Massachusetts Institute of Technology. Support for this research was provided by the Defense
Advanced Research Projects Agency of the Deparuncnt of Defense monitored by the Office of
Naval Research under contract NOO015-75-C-066 1 and N00014·83-K -0125. and by Digital
. Equipment Corporation of ~1aynard Massachusetts, with grants of equipment.
CA~1BRIDGE
MASSACHUSJ:n's INS1TruTEOFTECHNOJ.OGY
LABORATORY FOR COMPUTER SCIENCE
MASSACHUSErrS 02139

• • ~ ~ ~ • ~ .. ¥~ • ..'
Abstract
This document describes NIL. a New Implementation of Lisp. NIL is currently under
development on the DEC VAX under the VAX/VMS operattng system.
Acknowledgments
The chapter on defstruct is a worko\'er of. the chapter appearing in [3]. by Alan Bawden:
added in(lcclIracies are solcly the nUllt of GSB. howe\ er. The chapter on the loop maCfO is a
revision of an earlief published memo [5] which also has appeared in I -isp Machine manuals [12].
'1l1e chaptef on flm'ors was written in part by Patrick SobaIvarro.
documentation are the work of Christopher Eliot.
The editor and its
The interfaces to many functions and .fc'lcilities. and somc of the terminology used in this
document. ~lre taken or derived from thosc used in the ('0\1:\10' I.lSP manual [1]: in particular.
the tCl1llinology llsed for describing scopc and ex/clll in chapter J.
The section on format (section 19.6. page 187) is a reworking of a chapter appearing in [3].
pans of which had earlier appeared in [12] and are the work of Guy Sleele.
Dedication
This publication is dedicated to Randy Davis, may his 750 never crash.
Note
Any comments, suggestions, or criticisms will be welcomed.
network mail to BUG-NIL@MIT-MC.
Please send Arpa or Chaos
Those not on the Arpanet may send U.S. mail to
Glenn S. Burke
Laboratory for Computer Science
545 Technology Square
Cambridge, Mass. 02139
The Arpa network mail distribution list for announcements pertaining to f\;Il is normally used
for announcements about the facilities described here. Contact the author to be placed on it.
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Document History
Earlier versions of this document were distributed as NIL Noles for Release 0 (in two revisions).
and NIL Noles for Release 0.159. This update corresponds to NIL release 0.286, Lisp. system
version 286. It will be revised and reissued with each new Nll. release; because of the constant
changes, it is not the picturc·pcrfcct copy we would like.
Additional Publications
This manual, and other pubJic~ltions~ arc available from the J.ab for Computer Science
Puhlicmions office
MIT LCS Publications
545 Technology Squa~e
Cambridge. MA 02129
who should he contacted directly k)r bibUogr

NIL Manual
Summary Table of Contents
Sunlmary rrable of Contents
1. Introduction .
2. Dak1 Types.
3. Scope. Extent. and Binding .
4. Predicates ..
5. Programming Constructs .
6. Declarations .
7. Sequences
8. I.isis .
9. Symhols
10. Numbers
11. Characters.
12. Arrays.
13. Strings.
14. Hashing.
15. Packages
16. Defstruct
17. The LOOP Iteration Macro
18. The Flavor Facility
19. Input. Output. and Streams
20. Syntax. . .
21. Debugging and Melering
22. Errors. .. . .
23. Environment Enquiries
24. Compilation. .
25. Introduction to the STEVE editor .
26. The Patch Facility.
27. Talking to NIL ....... .
28. Peripheral Utilities. . . . . .
29. Foreign Language Interface.
30. What Will Break ..
References. ..
Concept Index. . .
Message Index. . .
Resource Index . •
Variable and Constant Index. . .
Function, Macro, and Special Form Index . .
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T.lbJc of Contents
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NIL Manu •• 1
Table of Contents
1. Introduction. . .
1.1 Conventions .. . . . . . . . . . . .
2. I )al~1 Types . . .
2.1 Numbers ....
2.1.1 Rarillflals. . .
2.1.2 "'loafing-point Numbers ..
2.1.] Complex Numbers.
2.2 Characters . . . .
2.3 Symhols . . . . . • . .
2.4 l.ists c:md Conscs . . .
2.5 Armys and Sequences.
2J) Structures. . . . . . .
2.7 Functions .•.....
2.8 Random .mernal Types. .
2.8.1 Minisubrs •.•..•.
2.8.2 Modules. . . . . . . .
2.8.3 I nlernaJ Markers. . . .
2.8.4 Unused Types. . . • .
2.9 Coercion . • . . . • . • .
3. Scope. Extent. and Binding •
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3.1 '..41mbda Application . . . . . . . . 11
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4. Predicates. . • . . . • • • .
4.1 Type Predicates ..... .
4J.l Type Specifiers .... .
4.1.2 Gcneral Type Predicates •.•
4.1.3 Specific Type Predicates .•
4.2 Equality Predicates • • • • • .
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5. Programming Constructs . • • . . . • • •
5.1 Compositions. • • • . .. • • • . • . • • • .
5.2 Definition Fonns. • • • • . • • . • • • •
5.2.1 Defining Functions. • . • • . . • • . •
5.2.2 Defining Macros. • • • . . . • •
5.2.3 Defining Variables. • . • •••••
5.2.4 ControHing Evaluation TIme. • . • . • • • . . •
5.3 Binding and Assignment . . • • • . • • . • • • . •
5.3.1 Dynamically Binding Variable Variables ..•.•
5.4 Conditionals . . . • . • . . • . • • . . • . . •
5.5 Function Invocation. • • •
5.6 Iteration Constructs. • • •
5.6.1 Mapping Functions ..
5.6.2 Othcr Iteration Forms •
5.6.3 BJock and Tagbody. . .
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Table of Contents
5.7 Non-I.ocat Flow ufControI ..
5.8 Multiple Values ....
5.9 Generalized Variables
5.10 Property Lists ...
6. Declarations . . . . . . . .
6.1 Local Declarations . .
6.1.1 The Special Declaration . . .... .
6.l.2 Declarations Affecting Vari~lble Bindings.
6.1.3 Declarations Affecting Compilation Strategies . .
6.2 Proclamations: Giuhat Dechlrations
6.3 Declaring the Types of ronns. . .
7. Sequences . . . . . . . . . .
7.1 Accessing Sequences .... .
7.2 Creating New Sequences .... .
7.J Searching through Sequenccs .. .
7.4 M iscelJaneolls Operations on Sequences.
7.5 Iteration over Sequences ..... .
7.6 Sorting Sequences . . . . . . .. . . . .
8. Lists . . . . . . . . . . . . . . . . . . .
8.1 Creating. Accessing, and Modifying List Structure.
8.2 Substitution . . .
8.' lJsine f .~sts as S~ts
8.4 Association Lists . .
9. Symbols ...... .
9.1 The Property List ..
. 9.2 Thc Print Name ..
9.3 Creating Symbols ..
9.4 The Value and Function Cells.
9.5 Additional Names . . .
9.6 Symbol Concatcntation ..
9.7 Internal Routines. . • . .
10. Numbers •.......
10.1 Types. Contagion, Coercion. and Confusion.
10.1.1 The Types . . . . . . . .
10.1.2 Contagion and Coercion.
10.1.3 Confusion ....... .
10.2 Predicates on Numbers ..
10.3 Comparisons on Numbers. .
. 10.4 Arithmetic Operations ...
10.5 Irrational and Transcendental Functions.
10.5.1 Exponential and I.ogarithmic Functions ..
10.5.2 Trigonometric and Related Functions. . .
10.6 Numeric Type Conversions •........
10.7 Integer Convcrsion and SpeciaJized Division. . .
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10.8 I.ogical Operations on Numbers .
]0.9 Byte Manipul~ti()n Functions.
10.10 Random Numbers .....
10.11 Fixnum-Only Arithmetic ..
10.11.1 Comparisons. ..... .
10.11.2 Arithmetic Operations ..
10,11.3 Bits and Bytes. . .. . .
10.11.4 'Inc Super-Primitives ..
10.12 Double-Float-Oniy Arithmetic ...
10.13 Decomposition of Floating Point Numbers . .
10.14 Implementation Constants
11. Characters. . . . . . . . . . .'. . . . . .
] 1.1 Pred icates on Ch.lractcrs. . . . . . .
11.2 Ch

NIL Manual
v
Table of Contents
16. Dcf.~truct . . . . . .
16.1 Introduction .....
16.2 A Simple Examplc
16.3 Syntax of def.~truct
16.4 Options to defstruct. .
16.4.1 :type. . . . .
16.4.2 :constructor .
16.4.3 :altcrant .
16.4.4 :namcd..
16.4.5 :prcdicatc
16.4.6 :print ..
16.4.7 :dcfault-pointcr
16.4.8 :conc-name. .
16.4.9 :inc1ude .... .
16.4.10 :copier .... .
16.4.11 :class-symboJ ..'
16.4.12 :sfa-function
16.4.13 :sfa-name ..
16.4.14 :sizc-symbo1.
16.4.15 :size-macro . .- .
16.4.16 :initial-offset
16.4.17 : but-first . .
16.4.18 :callablc-acccssors..
i6.4J9 :evai-when ......... .
16.4.20 :property .... .
16.4.21 A Type Used As An Option .
16.4.22 Other Options ..•.....
16.5 The dcfstrucl-dcscriplion Structurc
16.6 Extensions to dcfstruct . . . . . .
16.6.1 A Simple Example ...... .
16.6.2 Syntax of defstruct-definc-type .
16.6.3 Options to defstruct-define-type.
16.6.3.1 :cons . . . .
16.6.3.2 :ref....
16.6.3.3 :predjcate.
16.6.3.4 :overhead.
16.6.3.5 :named . •
16.6.3.6 : keywords . .
16.6.3.7 :defstruct-options • •
16.6.3.8 :dcfstruct ..•...
16.6.3.9 :copier . . . . . . .
16.6.3.10 :implcmentations. .
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17. The LOOP Iteration Macro
17.1 Introduction. . . . . . . .
17.2 Clauses. . . . . . . .' . .
17.2.1 Itcration-Driving Clauses ....
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NIL Manual
17.2.2 Bindings .....
17.2.3 Entr~mce and Exit.
17.2.4 Side Effects.
17.2.5 Values ..... .
17 .2.6 Endtest.~ . . . . .
17.2.7 Aggregated Boolean Tests.
17.2.8 Condirionalil.ation . . ..
17.2.9 Miscellaneous Other Clauses
17 J I.oop Synonyms ..
17.4 Data Types . . . • . . .
17.5 Dcstructuring •.....
17.6 'I'hc Itcrcllion Framework
17.7 Iteration Paths. . . . . • , .
17.7.1 Prc-Defined Paths ...
17.7.1.1 The Interned-Symbols Path
17.7.1.2 Seq uence Iteration. ... . . . .
17.7.2 Defining Paths ....... .
17.7.2.1 /\ 11 Example Path Definition .
18. Thc rlavor Facility. . . . . . . • ..
18.1 Introduction. . . . . . . . . . . . . • . . .
18.1.1 Object-oriented Programming ......•.•.
18.1.2 Objcct-oriented Programming Using flavors.. . .
IR.2 System-nefincci M~AAges . ... . ..
18.3 Message Defaults . . . . . ....
19. Input. Output, and Streams.
19.1 Standard Streams ....
19.2 Strcam Creation and Operations ...... .
19.3 Input Functions. • . •...
19.3.1 Ascii Input. . 0 • 0 • • • • • 0 ••
19.3.2 Binary Input . • • 0 • • • • • 0 ••
19.4 Output Functions. . •.•..• 0 ••
19.4.1 Ascii Output . . • . • • . • 0 • • • • ••
19.4.2 Binary Output ....••..•..•..
19.5 Fonnatted Output ....
19.6 Format 0 • • • • 0 • • •
19.6.1 The Operators • 0 0 •
19.6.2 Defining your own ..
. ..
19.7 Qucrying the User 0 •• 0
19.8 FHesystem Interface 0.' 0.' • • •••••
19.8.1 Pathnarnes • . • • • . .. • • • • . • • . . . .
19.8.1.1 Pathnarne Functions. '0 • • • •••••
19.8.1.2 Merging and Defaulting •••••...••••
19.8.2 Opening Files. . • . . • •.•••
19.8.3 Other File Operations. . ..•.
19.8.4 File Matching. • . • . . •
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Table of Contents
19.8.5 Loading files .................... .
19.8.6 filc Attribute Lists ................ .
19.8.7 Intcrnals for VMS Record Management Scrvices .... .
19.8.7.1 Data Stnlcturcs ...... .
19.8.7.2 RMS and Related Hacking. ...... .
19.9 TcrminalllO ............... .
19.9.1 Modifying the Terminal Characteristics ..
19.9.2 Making More Tenninal Streams
. ~. .
19.9.3 Display 'ITY Mcssages ..
20. Syntax ........... .
20.1 What the Reader Tolerates.
20.1.1 Backquote . .
20.2 'Inc Lisp Reader ... .
20.2.1 Introduction ... .
20.2.2 Reader Extensions.
20.2.3 Readtable . . . '. .
20.2.4 Alternative Syntax .
21. Dcbugging and Mctering
21.1 I-low of Control ....
21.1.1 Tracing. . . . . . .
21.1.2 Who does Wha~ and Where.
21.2 Examining Objects . . . .
21.3 Ucbug and Breakpoints . .
21.4 Metering ...... .
21.4.1 Timing. . . . . .
21.4.2 Function Calling .
21.5 System Management
21.5.1 An example . • .
21.5.2 "Source (Re)Compilation" ..
21.5.3 Information in Modules
21.5.4 Related Utilities .
21.6 Verification . . • • • •
22. Errors .....•...•
23. Environment Enquiries
23.1 The Host Environment . •
23.2 Mac1isp-Compatihle Status Enquiries .
23.3 Privileges. . . • .
23.4 Memory Usage . . • . . .
23.5 Time and Date . • • . . •
23.5.1 The Main Functions • • •
23.5.2 Printing Dates and Times.
23.5.3 Namings. . . . . • . • •
23.5.4 Timezones. . . . . . . .
23.5.5 Miscellaneous Other Functions.
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Table of Contents
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NIL Manual
23.5.6 Variations in Daylight Savings Time. . . . . . .
23.5.7 Internal Conversions . '0 0 ........ 0 0 0
23.5.8 Brain Damage . . 0
23.6 Job/Process and System Infonnation. . . . •
• • • • • • • • • • • • • " • • •
24. Compilation . . . . . . . . . . . . . . • . . .
24.1 Interaction Control. . . . • . . . . . . . . .. . . .
24.2 Efficiency. Optimization, and Benchmarking .•.•
.239
... 240
. .240
.241
.243
. 246
.246
249
25. Introduction to thc STEVE editor ..... • 0 • • • • •
25.1 Introduction. . . . . • . • . .. . . . . . . . . 249
25.2 Gctting Started • . . . . . . . . . . . . . . . 249
25.3 Editing Files ... 0 • • • • • • • • 250
25.4 Modifying the buffer. . • • . • . • . 254
25.4.1 The Simplest Commands . . • . . . . . . . . . . 254
25.4.2 Now that you know the Simplest Commands . • . . . . 255
25.4.2.1 Numeric Arguments" .•.... • · • . . . . . . • . . . . .. 255
25.4.2.2 Control-X. . . . . . • . • 0 0 • • • • ". • • • • • • • • • • • • • • • •
25.4.2.3 Mcta-X and Control-Meta-X. . . . . . . . . . . . . .
256
. 256
25.4.2.4 Marks and Regions. . . . . . . . . . . . . . . . . . . . . . . . . . 257
25.4.2.5 KiUing and Un-kiJIing . • . . eo • .. • • • • • • • • • • 0 0 • • • • • • • • •
25.4.2.6 List Oriented Commands. • . . • . · • • . . . . . . .
257
. 258
25.4.2.7 *more* • . . . . • · . • . . • • . . . . . • . . . . . . . . . . . 258
25.4.2.8 Aborts. . ." . . . • • • • • . • . . . . '. . • . . . . . . • . . • . . . . . 258
25.5 Major Modes . . . . • . 0 • 0 • • • • • • • • • 0 • • • • • • • • 0 • 0 •
25.6 Help and Self Documentation • • • . • . . • . . . .. • . • . • . . . . . . . .
258
. 259
25.7 GJossaryofCommands • ..• • • • 0 • 00 0 • • •• 0 • • • • • • • • .260'
25.7.1 Special Character Commands .... • .... 0 •••••• 0 ••• 0 • 261
261
25.7.2 Contro) CharaclerCommands ... 0 • • • • • • • • • • • • • • • • •
25.7.3 Meta Key commands. . . . . . • . . . . • . • • . • • . . . . . . • 264
25.7.4 Control-Meta Commands ..•. 0 •• • • • • • • • 0 • • • • • •• 0 266
25.7.5 Control-X Commands. .•. • • · 0 • • • • • •••••••••••••••••• 268
25.7.6 Meta-X Commands. . . 0 • • • • • • 0 • • • • • • • • • • • • • • • • • • • • • 271
25.8 Extending the Editor. . • • • • . . • • • • . • . • . • • • • • • . • • • • . . . 0 • • • 274
25.8.1 Editor Functions • 0 • • • • • • • • • • • • • • • • • 0 • • • • 0 • • • • • • • • 0 0 • • 274
25.8.2 Editor Objects • . • • . • • • • • • • • • • • • • • • • 0 • • • • • • • 275
25.8.3 Other Functions and Conventions. 0 • • • • • • • • • • • • • • 0 • 0 • • • • • 277
26. The Patch Facility. • . • • • • • • • • • • • • • . • • • • • 0 • • • • • • • • • • 0 280
26.1 User Functions . . . • • • • • • • • • . . • • • • • 0 • • • • • • • • • 0 • • • • • • • • • 281
26.2 Patch System Infonnation • . . • • 0 • • • • • 0 • • • • • • • • • 0 • 0 • • 0 0 • • 282
26.3 Adding Patches . . . . • • . • • • • • • • 0 • • • • • • • • • 0 • • • • • • • • 282
26.4 Defining Patch Systems. • •• • • • • . • • • • '0 • • • • • • • • • • • • • .284
27. Talking to NIL •• · • • · • • • • • • · • . • . • • • • • • • • • • • • . • • • . • . . • . 287
27.1 Stanup • • •. • .• • • .• • • • • . • . . • • • • •••..• 0 • 0 • • • 287
27.2 The Toplevel Loop. . • 0 • • • • • • • • • • • • • • • • • • • • • • • • • • 288
27.3 Entering and Exiting NIL • . • • • · • • • . . • • • . • . . . . • • •. . . 288
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NIL Manual
ix
Table of Contents
27.4 VMS .. 0 .. 0 ..•.• 0
27.5 Installation . . . . . 0 • • •
27.6 How the NIL Control Works
28. Peripheral Utilities. . . . .
28.1 The Predicate Simplifier ...
28.2 A Mini-MYCIN. 0 0 ••••
28.3 Mac1isp Compatibility for Macsyma. .
29. Foreign Language Interface ..
29.1 Introduction. . . . . . . . .
29.2 Kernel and System-Services 0
29.3 VMS object files ...
29.4 Data Conversion ..
29.5 lower level routines .
30. What Will Break ....
30.1 What Broke Since Release 0.259. . .
30.2 Future Changes. . 0 • 0 • 0 • 0
30.2.1 Default floating-Point Fonnat .
30.2.2 New Package facility .. 0 0 . 0 •
30.2.3 Vector-push and Vector-push-extend 0 •
30.2.4 Multiple Values .. 0 • 00 •• 0
30.2.5 Variable Naming Conventions 0 0
,0 ").6 Otlrhaee Col1~ction. .
30.2.7 Error System. 0 •
References. 0
Concept Index.
Message Index.
• • 0
Resource Index . 0
Variable and Constant Index. •
Function. Macro. and Special Fonn Index • • •
• 0 291
0290
o .293
· . 295
· .• 295
• 0 • 296
· .297
· .298
· • 298
· 0298
· .. 299
• 0 299
· . 300
· • 301
. ..... 301
....• 303
· . 303
.303
• 0 303
. 303
· .305
.30S
o 0 305
o 0 307
o 0 0 308
• 0 0 310
· •. 311
o 0 • 312
.•.• 314
23-DEC-83

---------------------------------------------------------------------------------------

NIL Manual 1 Introduction
1. Introduction
NIL. which stands for New Implementation of Lisp. is a dialect of LISP which runs on the
DEC VAX. NIL currently runs under the VMS operating system. It will likely be converted. to run
under U~lX (TM) at some point, but there is no effon underway to do so right now.
NIL is a dialect of CO\1MON LIst). COMMOJ\ LISP is essentially a formal specification of the
LISP language such that programs which confonn to that specification may be transported without
modification from one CO\1\10~ LISP implementation to another, and be expected to run
compatibly. As of this writing. the CO\1\f0~ liSP manual has just gone to press: this manual has
therefore den'loped into documentation of a subset of C()\1\tO~ IISP facilities which are currently
supported by :\11.. and a large number of ~II -specific things.
This document schi/ophrenicall, attempts to cover three areas. One is "primer"
document.ation: those things which must be known for any programming to get done. In this
case. aucmpts arc made to point out what of these things are ('0\1\10:\ LISP compatible. Another
is the set of things which migl;~ he expec-ted to change incompatihl), du£' to (,0\1\10' liSP
conversion. The third is those wllich are part of the :\11 core Virtual lllac/till£'. as it is heing
de\cloped more fonnally. These include. for example. functions like %string - replace. \\hkh are
sUiLtble low-level primitives for a VAX (or other byte-machine. like perhaps an 1B\1-J70) to
provide. Lastly, there are certain parts of ~IL which have undergone large amounts of recent
development. and are fairly stable. and which· may provide functionality for lIsers in various
domains: the 1/0 system. for example. Much of the pro\'ided documentation will he of things
witidt ,uc ub!'ll:clIciy iuw-ic\'ci: ~omelimes. this is (0 point out piaces where me implementatIon
falls short of the design: often too. to document these t(lr those who may find it useful,
debugging. or in perfonning implementation-dependent activities: and occasionally, to explicitly
note how the implementation differs from the general and portable semantics (as in the case of
numbers and eq).
1.1 Conventions
All otherwise unqualified rational numbers in this manual are in decimal, not octal (as has
been the practice in certain other manuals. notably [9] and [12]). Special qualifying syntax for
forcing the interpretation of rational numbers in other radices is described in section 2.1, page 3.
There are a couple conventions for the fonning names of functions and variables coming into
use from within the COMMON USP community.
Generally. variables whose values are special and which may be modified during the course
of program operation have names which begin and end with an asterisk; for instance,
-package-. Lexical variables, and constants defined with defconstant (page 24), are nonnally
named without these asterisks. For instance, NIL defines the constants pi and most-positivedouble-float.
This is a convention only and does not affect the operation of the I'lL interpreter
or compiler; however. the possibility exists tJlat (in tJIC future) the compiler will lISC the presence
or ahsence of such asterisks to choose a course of action if it encounters a free reference to an
undeclared variable. (Special and lexical variable reference is discussed in chapter 3, page 11.)
MC:NII.MAN:INTRO 18
23-DEC-S3
.
, - ~ -
,"", '.. ' .':: : ~ ..,'-. - ,: -'< c' _ . .'

Cotl\'cnliot1s 2 Nil. Manual
'n1e names of predicate functions in!\u, and CO:\fMON LISP are typically fi)nned by suffixing
the character t~p" to the end of a descriptive name. For instance.consp is a predicate which is
true if its argument is a cons~ and lessp (which actuaUy is a MACUSP. not COMMON USP.
function) compares numbers and (when given two arguments) returns t if the first is less than the
second. If the name itself is hyphenated. then "-pit is suffixed: upper-case-p is a predicate
which tells if a character is upper-case. If, however. the predicate name is fonncd by prefixing a
specializing name to an existing predicate name, then the final t.p" would not have hyphenation
added to it: string-Iessp is a predicate can be used to compare strings using a standard collating
sequence. the name heing fimned by prefixing "string-" to 'tlessp". There are. of coursc. many
exceptions to this. and this convention does nOl eliminate all ambiguity. but it helps. A goud
numher of ~II functions did not fi)Uow this convention in earlier versiul1sof. ~II: many of these
h~l\'e heen fixed. mld the old names made synonymous with the new names for the time being.
MC:NJLMAN;INTRO 18
23-DFC-83

NIl. Manual 3 I )ata Types
2. Data Types
This chapter provides an overview of some of the data types used in NIL. their uses. and
their syntax (their prillted representatio1l). Those not strongly familiar with LISP should go over
this lightly to get some idea of the sorts of objects which NIL offers. and proceed to the next
chapter: others might want to read it anyway. to see what NIL provides which may differ from
other LISP dialects. Most of the sections here have later chapters devoted to them. which give
much more complete infonnation on the types. how they may be used. and the functions which
can manipulate them. Also. more complete 'information on the syntax used for these types is
presented in chapter 20. page 213.
2.1 Numbers
The I'll. (and COM\101' LISP) hierarchy of numeric,l) types looks like this:
number
rationa j
intE:ger
fixnum
bigntJm
ratio
float
short-float
siiigle float
double-float
long-float
complex
Collectively. the non-complex numbers are referred to in NIL as the type non-complex-number:
the tenn real is not used because of potential confusion with floating-point. Note that there is no
guarantee that the above types might not be further subdivided or grouped for the convenience of
the implementation.
2.1.1 Rationals
The integer data type is intended to represent mathematical integers. There is no magnitude
limit on them other than that imposed by memory or addressing limitations.
In NIL. those integers which can be fit in a 30 bit field in twos-complement are fixnums.
which are represented in such a way that no storage is consumed. For integers not in this range.
bignums are used. Generic arithmetic functions automatically choose the appropriate
representation.
The printed representation of integers ordinarily uses decimal notation. optional1y preceeded
by a sign character and optionally followed by a decimal point. The sharpsign reader macro
(section 20.t page 214) may be used to input rational numbers in other radices; for instance.
MC:NILMAN;TYPES 36
23-DEC-83

Numbers
4 NIL MimuaJ
259
259.
#0403
#blOOOOOOl1
; Thc integer 259
; 'Inc integer 259
; entered in {leta!
; entered in binary
A ratio is the type used to represent non-integer rational numbers. It consists logically' of
integer components which arc its numeralor and drlllJlltillolOr (which arc accessible by functions of
the same names). °rbe exteTmd intcrf,lCc is defined such that a ratio will always appear to be in
r{'duced fonn (whether or not it is). and the denominator will alw,.ys be positive. (CO\1\10~ I.ISI)
sei'. it can't be I.cro, infinity freaks.) 'nlC ct.rithmetic nmtincs which deal with rational numbers
tranpar{,lltly C(}f1\"{'rt between ralios. bignums. and fixnumsas aPllfOpria\c. Ratios itrC d{'notcd
separating the numerator and the denominatory by a I: thus. the ratio three-halves is 3/2.
2.1.2 Floating-point Nunlbers
CO\1MO~ LISP allows for four kinds of floating-point representations, which must meet the
filltuwing critcria:
Format ~inimum PreCision Minimum Exponent Size
Short 13 bits 7 bits
Single 24 bits 8 bits
Double 50 bits 8 bits
long 50 bits 8 bits
Nn !lrovid~:111 nf these fnrmat~ with th(' f(ll1(lwing specs:
Type Precision Exponent
short-float 19 bits 8 bits
single-float 24 bits 8 bits
double-float 56 bits 8 bits
long-float 113 bits 15 bits
The long - float type requires microcodc support to avoid software emulation.
Floating-point numbers in NIL are syntactically distinguished from integers in that they must
have a decimal point followed by at least one digit. (This is more rigid than the COMMON USP
specification.) So. for instance, 10 and 10. are both the integer ten. but 10.0 is floating-point 10.
The various fonnals of floating-point number are syntactically distinguished by the use of the
character used in exponential notation. For example. 10.OdO is double-float ten; 10.050 is shortfloat
tcn. 10.010 is long-fioat ten. and 10.0e0 is single-float ten. When exponential notation is
not used. the type of float is determined by the user-modifiable variable .read-default-floatformat.
(page 72). COMMON USP specifics that the default type of float is single-float, both for
readin and the values of various irrational or tranccndcntal mathematical functions when they are
given rational arguments (c.g.. sqrt). However. in NIL. the default is currently double-float,
because this NIL release is the first to supply any (onnat other than double-float. The default
;"ill be changed in a future release.
MC:NlI.MAN:TYPES 36
23-()EC-83

Nil. Manual 5 Characters
2.1.3 Complex Numbers
Complex numbers in NIL represent a point in the complex plane in cartesian coordinates.
Their printed representation shows these coordinates:
/lC (rea/part imagparg)
The real and imaginary parts may be extracted with the reaipart and imagpart functions.
The real and imaginary components of complex numbers must both be either rational
numbers, or floating point numbers of the same floating-point fonnat.
Rational numbers and complex numbers with rational components collecti\"el~ constitute the
gaussian-rational :\11 data typc. Many. but not all. rational number functions ha\'e heen
extended to operate on gaussian rationals in Nil. for instimce numerator. denominator. and
mod. In order to provide what we call a seamless ex/ellsioll of the rational numbers to the
complex plane. a gaussian rational with a zero imaginary part is not of type complex. but just
the rational number. This interconversion may be compared with that which interconverts between
fixnums and bignums a~ necessary. Gaus~ian rationals which have integer components (i.e..
integers. and complex nt.:.,nbers with integer components) are the Nil type gaUSSian-integer.
which is of course a subtype of gaussian-rational. Certain integer flmctions in :'\11. have been
extended to operate on gaussian integers: these include gcd. oddp. and evenp. The gaussian
rational and gaussian integer extensions in 1\11. are not defined by CO\1\10~ l.lS}>. and should
therefore be considered experimental and potentially subject to change. For this reason. feedback
on their usage and utility is desired in order tJlat these extensions can be evaluated.
Complex numbers with floating point components always have components of the same
floating-point format. Such a number is always of type complex. even if the imaginary part is.
zero.
2.2 Characters
NIL provides a data type for representing characters. Characters are the things one
manipulates when doing "character 1/0" on streams. They are the things one gets out of, and
puts into, strings. Having a separate data type allows them to maintain their identity within the
lisp (as opposed to being an interpretation placed on fixnums, for instance). Chapter 11 is
devoted to this.
Characters in NIL use # \ syntax for input and outpu~ as shown below. Note that if the
character after the # \ stands alone. it is taken literally. If it occurs after a prefix such as
"control- n , then it will be treated like an ordinary token, so may need to have a preceding
backslash to inhibit case translation or just to allow proper token parsing.
'\a
: Lowercase "a".
'\A
; Uppercase "a".
'\Control-a
: Uppercase "an, with the control bit.
/I\Meta-\a
: Lowercase "a", with the meta bit.
Some characters have names, which may be lIsed in place of the character itself:
/I\Rubout
;'nle "ruhout" or "delete" character
#\Hyper-Space
: The "space" character with the hyper bit
MC:NIl.Mt\N:TYP~S 36
23-DEC-83

Symbols 6 Nil. Manu,,1
Only a subset of all possible characters are a110wcd to be contained in strings. These comprise
the string-char d.tta type. It hClppens that in NIL these are tJlose characters which have no font
or· bits attributes (both are 0).
2.3 Symbols
Symbols are what are used as names in lisp_ They can name functions. and variables (the
two uses of which are syntactical1y distinguishable by the . LISP evaluator). Symbols have a 110mI'.
also called the print /lome or p"ome. which is a string containing the chamcters used in the
printed representation of the symbol. A symbol also has a propert)' lisl or plis! associated with it.
Thi~ is a list of ailefll,lting "indicators" 411ld "\·,tlues". allowing one to sture unidirectiunal
associations on the symhol. A symhol also has a package. which points to the "name spacc" it is
associated with (chapter IS. page 121)~
The symbol nil is special. It is used both to represent booleoll folse. and the empty Jist. Its
alternate printed representation is· O. the empty Jist It has the data type null. which is both a
subtype of symbol and a .subt~l)e of list and is the only object of that type. ltli value is not
allowed to be changed. OtherwIse. it is lreated the S{.lme as other symbols (it h.1S a property list
etc.).
The symbol t is used to represcnt boolean lruth. Its value is also not allowed to be changed.
Symbols arc often used as keywords. Because of the existence of multiple namespaces
(packages). t11is might present a problem because two symbols read into different namcspaces
might not be the same. This is solved by haying special kCYM'(}rd symbols. or just keywords for
short. A symbol which is typed in preceded by a colon (and nothing else) is read into the
namespace (package) for keywords. Thus. an symbols so designated are the same (they are eq).
Keywords are self-evaluating, and their values are not allowed to be modjficd~
NotationaUy. tokens which cannot be interpreted as anything else are taken to be symbols.
except that tokens consisting entirely of unslashified dots are supposed to cause a syntax error~
Thus. , .Oe + 4 will read as a floating-point number. but , .Oe + 4a will read as a symbol. More
complete details on input syntax are in chapter 20. page 213.
2.4 Lists and Conses
A cons is the type which makes LISP what it is. In simpler lisps. it may be the only data
type which can be used to associate more than one object A cons makes a binary association: it
has two components. its car and its cdr, which are accessed by just those functions. It is thus
the datastructure of choice for representing binary trees.
A list. when considered to be a data-type, is the union of the types cons and nutt-that is.
it is either a cons. or the symbol nit (the empty list). That is why the alternate printed
representation of nil is O. (See section 20.1. page 214 for exposition of the printed representations
of cnnses and lists.)
MC:NII.MAN:TYPES 36
23"DEC-83
, " ,;":. i -,~;~;' ,; ',< ,~',
~ "."-
"':
,i "~"~~'~;: co;': -- ," ,',' < :'.,:,,"" ,,' ,•••

-
NIL Manual 7 Arrays and Sequences
Often, a list is a conceptual sequence which has a discrete end. In this context. the cdr of
the last cons of the list must be nil. In text (and error messages), the phrase "proper Jist" is
used to distinguish between just a cons (or nil) and an actual list whose final cdr is nil. For
instance. the cons
(a . b)
is of the type list. but if given as a list argument to the member function (page 61) would cause
an error which would say that it was not a proper list.
2.5 Arrays and Sequences
Arrays in 'II. are a ,ery geneml type. One dimensional arrays are the type vector. Arrays
can he specialized as to the types of elemenl'i they may contain. A one dimensional array (a
vector) which can only contain "string characters" (see the string-char-p function. page 19) is a
string. A one dimensional array which is allowed to hold only objects of type bit (that is. the
integers 0 or 1) is a bit vector. Arrays are discussed fully in chapter 12. page 103.
The type sequence is th;! union of the types list and vector. There are a large number of
Sfl/UfllCf jUllctiollS in 'II. which operate on hoth Jists and vectors, \'iewing either as just a
sequence of ohjects. One therefore has a\'ailahle the same general sequence operations. to be used
on whatever particular type of datastructure was chosen for the task at hand: they may be lists,
to make adding. delcting. splicing. etc.. easy, or \'ectors of a particular type suitable for the
application-strings. bit vectors, etc. The functions for operating on sequences are described in
ch:lpter 7, page 4R.
2.6 Structures
NIL provides a structure or record definition facility. This is supplied hy the defstruct
function (page 125). which is essentially the same one used in both MACLlSP and LISP MACHINE
LJSP. In ~IL. the nonnal way defstruct is used defines a type, and the structures creatcd can be
distinguished with typep. Additionally, such types interface to the NIL flavor system, which may
be used to give them methods for such things as how they should print and pretty·print
2.7 Functions
There are several different things which can be "functions" in NIL. Most basically, there is
the type compiled-function (also known as subr). This corresponds to a function created by the
NIL compiler. or part of the NIL kernel. It may also be created "on the fly" for the purpose of
interfacing compiled code to interpreted code; in NIL, functional evaluation of an interpreted
function will result in an object of type compiled -function.
Functional objects which implement "environment transfer" (which is discussed in a later
chapter) are of the type closure. The most commonly seen specialization of this type is that used
in the interpreter. the type interpreter-closure.
MC:NILMAN:TYPES 36
23-DEC-83
", - - ' , ',' - " -,' -'" ' '-. ' '-::'. - . ~ , '
'~:~>- -, ',:: .. ':' ' ... -~ '

Random Internal Types 8 NIL Manual
2.8 Random Internal Types
Here are some of the internal1y used types in NIL . While they should generally not be seen,
they may pop up on occasion either themselves or as a result of errors.
2.8.1 l\1inisubrs
lbe minisubr type is somewhat gratuitous: it win be flushed as a separate type someday. and
its type bits reused by something more uscthl. A millisubr is a special rOlltine within the 1'11.
k~rnel: Stich routines arc caned with the VAX JSB instn.ctioll. However. they tend to have
various assuned
2.8.2 Modules
A module. as a type. is the structure used by Nil. to contain a collection of compiled
functions and the constants and jat~lstructures they ·reference. When the cumpiler compiles a file.
it produces a module. When the garbagecollcctor (haha) relocates things. it rehlC,ttcs the module
as a hlnck. The use of the name module for this primilhe dalHstnlcture is it bit pretentious .. so it
will probably be called something like compiled-code-modufe in the future.
2.8.3 Internal Markers
The type si:internal-marker is used for variolls things in 1Ioi1L. none of which should
ordinarily be visible to (or touched by) the user. Objects of this type are meant to be checked
for by things like the debugger and garbage-collector (to. for instance. parse stack frames). and
manipulating them out of context wiUconfusc tllese programs.
These objects print out as #!
#fAFM-31
#fPC"MARKI
#!DOUBLE-FLOAT-MARK!
#!NULL-ARGI
followed by the name followed by!. For instance,
; Stack marker for 3-arg function
; call frame
; Next slot on stack is a PC
: Next two stack entries are the
; representation of a double-float
; Stack slot is for an argument which
has not yet been computed,in a
: function caU frame.
MC:Nll.MAN:TYPES 36

NIL Manual 9 Coercion
2.8.4 Unused Types
There are a number of unused type codes in NIL. Certain internal routines. upon
encountering them. bomb out to the VMS debugger because your NIL is then undoubtedly lOSing
its lunch.
2.9 Coercion
coerce o~;ecl Iype
If ol~;ccl
is already of the type 1),l'e. then it is simply returned: otherwise, it is COI1\ ened
to be of that type.
Only certain forms uf coercion are defined. coerce wiJI perform coercion of one sequence
type to another: its capabilities in this regard are similar to those of concatenate (page
50). Note. however. that concatenate will always return a copy of the sequence.
whereas coerce will only create a new one if object is not of the proper type already.
coerce also allows some non-sequence coercion< with the following types:
float
Coerce the object to a floating point number. If object is already a float, It IS
returned: otherwise. it is coerced to the default type of float (double-float). See
float. page 78.
short-float
single-float
double-float
long-float
Coerce the object to that particular type of floating point number. Again. this is
similar in functionality to what may be obtained by giving float a second
argument.
complex
object. which must be a number. is coerced to a complex number. If it is
already complex. it is returned. If it is rational, it is also returned; this is
because complex numbers with rational components and a lero imaginary part are
automatically reduced to rationals. If, however. it is a floating-point number,
then a complex number with object as its real component and a floating-point zero
of the same fonnat as object as its imaginary component, is returned.
(complex float)
(complex short-float)
(complex single-float)
(complex double-float)
(complex long-float)
Effectively, these are like coercing the number to complex, and then returning a
complex number whose realpart and imagpart have been coerced to the specified
floating point type.
character .
Conven object to a character. This coercion is only defined for integers (see intchar.
page %). symbols one character long, and vectors whose dement-type is a
subtype of character (i.e., character vectors and strings). Moreover, in the
MC:NII.MAN:TYPES 36
23-DEC-83

Coercion 10 Nil. Manual
integer case. an error is signalled if the coercion does not succeed (Le.. int-char
would return nil when given the integer abjl'l'I).
Note that coerce docs not providc for cocrcion to rational or integer types. This is
because the issuc of what to do about truncation OT rounding is a· matter of. the intent;
the functions rational (page 78) and rationalize (page 78) may be used to convert
numhers into rational numbers, and the functions floor, ceiling. truncate. and round
(section 10.7, page 79) are useful fix converting both floating-point numbers and ratios to
integers with various sons founding behaviour.
coerce docs not accept .. 11 of the gener~ll fonllsof type that it shuuld: however. must the
simple fOrmals. and cert;linJy &111 tlwse th&l( arc listed clbo\'c. arc handled properly.
When compiled. calls to coerce with a conswnt second argument arc changed by the
compilcr into calls to a routinc specific to the task: a few of these, most notably the
conversions to (non-complex) floating p()int, arc handled especially efficiently.
Thcre arc a number of nthcr functions which perform specific types of coercions.
instance. string will cocrcca sy~nbol or a string to a string.
For
MC:NILM!\N:TYPES 36
23-DEC-83

NIL Manual 11 Scope. Extent, and Binding
3. Scope, Extent, and Binding
The NIL interpreter uses lexical seoping. What this means, simply. is that variable references
which are "textually within" the code which binds them. are vaHd. Those references which are
not "textually within" the binding form are not, and will (typically) cause unbound-variable errors.
Consider the definition
(defun make-associations (keys single-value)
{mapcar "(lambda (key) (cons key single-value» keys»
which takes a list of keys. and returns an association list associating all of those keys with the
same single value (perhaps for usc by assoc). The first argument to mapcar. the lambda
expression. is technically a function. (The #' construct is explained hclow.) It is. however.'
textual1y within the binding of the argument Single-value. so that variable reference is lexical.
and that function works in Nil. as desired. Consider the alternative form
(defun make-associations (keys single-value)
(mapcar ,'make-one-association keys»
(defun make-ane-association (key)
(cons key single-value»'
which might appear to be equiva\ ~nt. The reference to single-value in the definition of makeone-association
is nol textually within the binding of that variable. hence appears "free".
Although this function (in the absence of extra geclarations. as described below) would function
"properly" in the MACLISP or IlSP MACHINE LISP interpreters. it will not in 1'IL. It is interesting
to note that (again without special declarative information) both the MACUSP and LISP MACHINE
LISP compilers will treat the second example as an error (or at least produce incorrect code),
because although the interpreters do not enforce lexical scoping niles, code is compiled that way.
A short note may be in order on the # ' construct which appeared above. # ' is an
abbreviation for (function ...), just as ' is an abbreviation for (quote ...).
In MACI.ISP. the two
are equivalent. Howe"er. in ~1I. (and to some extent in l.ISP MACHINE I.ISP too), use of this
special form is necessary to cause the proper (functional) interpretation of the fonn being
evaluated. In fact. in the make-associations example. it is that special interpretation which
makes the lexical reference to single-value "work". If quote was used instead of function, the
example would not work as desired. function (or # ') need not just be used around lambda
expressions. It may also be used around function names (as in the second make-associations
example). The effect of evaluating (function name) is equivalent to what the interpreter does
when it "evaluates" name in the function position of a list being evaluated.
NIL does not restrict one to using only lexical seoping rules. It is possible to declare to NIL
that a variable is special, and should be able to be referenced by code not textually within the
binding construct Or. perhaps a variable should have a global top level value and not be bound
anywhere. or maybe even have a top level value. and be bound in some places. This is the
purpose of the special declaration, which NIL implements compatibly with COMMON LISP, and
which is about the same as it is in USP MACHINE USP and MACUSP.
Most of the time. special variables are declared to be special globally. This means that the
NIL interpreter (and compiler) will always treat the variable as being special. even if there is no
declaration for it at the place it is bound. As a matter of style. variables declared special are
usually given names which begin and end with the character • so that they can be visually
MC:NILMAN:BIND 27
23-DEC-83

Scope. Extent. and Hinding 12 Nil. Manu411
distinguished from more "ordinary'· lexically scoped variablcs.
variable special is with defvar (p41ge 24). ror instance.
(defvar -leaves-)
(defun find-alI-leaves (tree)
(let (-leaves- nil»
(find-all-leaves-l tree)
-leav.8s-
) )
(defun find-all-leaves-l (tree)
(cond «atom tree)
; Empty sctofleaves
; o rO\lcl over the tree
; And return the leaves found
One way to globally declare a
(cond «not (memq tree -leaves-»
(setq -leaves- (cons tree -leaves-»»)
(t (find-all-1eaves-! (car tree»
(find-all-leaves-1 (cdr tree»»)
There are more esoteric (or SCIIEMIHike) ways in which the above could have been perfunned.
without the. usc of the special variable -Ieaves-. but the above is fairly straightforward. fairly
effident. ,md will also run (both k terpreled and -compiled) compatibly in MACUSP and !.lSI'
MACHINE I.ISP.
The above intuitive (or. if you prefer. hand-waving and vague) description can now be used
to more fonnally define the tenns of scope and extellt which are used to describe the accessibility
and lifetimes of things. of which variable bindings are one instance. The scope of something tells
where it may be validly referred to~ To say that something has lexical scope then means that it
iHay UC U)CU cJllywiaclc ·'i.cxluaiiy'" within Lhc conSlfUct which "creatcs" the objcct (e.g.. the
lambda-expression which binds a variable). Note that this docs not in itself imply that the
reference becomes invalid if that construct is exited. That dimension is the extelll of the object.
which tens the lime during which the object (e.g.. variable binding) is valid dynamic extent
means that the object (reference) is only vaHd during the execution of the construct. illdefillite
extellt means that there is no such limitation. Variable bindings in the NIL interpreter (which are
not special) have lexical scope and indefinite· extent lbismeans upward funarg capability.
indefinite scope means that there is no restriction on wbere a valid reference may occur from.
This is the case with special variables; the "free" references may be made from any piece of
code. The bindings of such variables. however, have only dynamic extent; they become invalid
(are "unbound") when the binding construct is exited. This combination of scope and extent,
which is quite common, is· referred to as dYllamic scope.
Now, for the pragmatics. The current NIL compiler actually only implements local scope
instead of lexical scope. Its capabilities lie only in dctennining when it is losing. In many cases,
this· docs nOl matter because the constructs being used are expanded out into other construc~
making the references local. This is what happens for mapcar, for instance: in the construct
(let «22 (computate»)
(mapc #'(lambda (x) (mumblify x 22» some-list})
the reference to zz within the lambda expression is a non-local (but lexical) reference. That
expression is recoded by the compiJer~ however. as an iteration without a separate function. in
which the reference become local.
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N II. Manual 13 I.ambda Application
reference This is actually a moderately standard way to handle .lexical variables: rewrite
the f(lnn when possihle to CilUse the reference to become local. The MACI.lSP compiler
docs this with the mapping functions: even if tJ1e open-code-map switch is turned off, if
such a reference occurs it will expand out the iteration to al10w the local reference.
Environment transfer is implemented with closures. A closure is essentially an encapsulation
of a function. and some ponion of a binding environment. The closures with which lexical
environment transfer is perfonned in the interpreter. interpreter closures. bundle up the lexical
environment as of tJ1e time of their creation. Thus.
(setq fn (let «x 5» (function (lambda () x)})}
=> #
(funcal1 fn)
=> 5
One may test fln" ~l closure in g.eneral with (typep x ·closure). or with the closurep predicate
(page 19).
Nn actually has the capability for giving "dvnamic" variables iudefilli/(' extent. '1l1is can be
used to implement old-tashioned closures as creaLj by tJ1e Lisp Machine closure function (which
exists in 1'11.).
In NIL. what has been said for variables as far as scope. extend. binding. and shadowing is
concerned. is equally true for fUllctions. Variable value and function value are handled in
virtually identical fashions. The primary differences between the two are that the interpreter does
new toplc"el specia1 variable value when the variable is not globally declared special), and the
compiler makes its special assumption quietly.
The design of the ~I1. binding mechanism is described by White in [13].
3.1 Lambda Application
Application of a lambda expression in NIL is much like that of LISP MACHINE LISP. A lambda
expression is of the general fonn
(1 ambda lambda-list {declaration}. {fonn}.)
In the simplest case. lambda-lisl is a (possibly empty) list of variable names, which are the fonnal
parameters to the lambda expression when it is treated as a function. There must be as many
arguments to the lambda-expression as there are variables. Thus.
«lambda (a b c) (list a be» 1 2 (+ 3 4»
=> (1 2 7)
TIle lambda-list may also contain special symbols which begin with the character &. These are
·often called lambda list keywords. but they arc "keywords'· only in the general sense. i.e.. they
are not typed in with a preceding colon. They are typically used to drive the matching of the
fonnal parameters (variables) in me lambda list with the values they should be bound to. There
are basically just four such keywords, each of which is optional. and which should appear in the
order they are shown in:
&optional
'The items from the &optional to the next&-keyword (or end of the lambda-list) describe
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1.4JJl1bda Application 14 NIL M4mual
optional arguments to the function. F..ach such item may be of one of the following
thrms:
variable
)f a corresponding argument is supplied. then variable wi1l be bound to that.
Othcrwisc. it will be bound to nil.
( variable)
Samc as an is01ated variable.
( variable inil-jonll)
If there is a corresponding argument. then l'ariablc is bound to thal. If not. then
inil-/iJrm is c"(lluated. and l'ariab/r buund to that result. Thc evaluation of iltiljimJl
is performed in ,til environment where all of the \'4lriHhlcs in the lambda 1ist
to the left of this one have been bound alreCldy.
( roriob/(' il1il-}("-1I1 illil-p-"ar)
Just like tJ1C ,previous fnnnat. Additionally. illit-p" var will be bound to t if there
was an argument supplied. nil if not.
& rest
There must be exactly une item between .;t 1 &rest keyword and the next &-keyword (or
the end of the lambda-list). This variable is bound to a list of all the remaining
arguments to the function.
&key
TIle items between &key and either &aux or the end of the lambda-list describe
keyworded arguments to the function. "lbese are arguments which are passed by keyword
rather than by position: when given, it must be preceded by the keywurdnaming which
argument it is. The function flU is defined with the lambda list
(sequence item &key (start 0) end)
which means it takes two required arguments (sequence and item). and two keyworded
arguments (slarl and end)_ lbe calls
(fill sequence new-item :start start :end end)
(fill sequence new-item:end end :start start)
are effectively the same. An keyworded arguments are by default optional. The
specification of a key worded argument in the lambda list is nonnaUy the same· as that of
an optional argument; thu~ if no :start keyword and associated value is specified in a
call to fjIJ. the Slar! parameter defaults to 0, and for elld, the default is nil. The name
of the variable is used to generate the keyword which flags that panicular parameter.
AddilionaHy, with the non-atomic fonns of optional parameter specification. a list of the
actual keyword which should be used and the variable to bind the argument to may be
used instead. For example, if it were desired that the keyword :start be used to flag the
starting index, but that the fonnal parameter be named i, then the lambda-list could have
been written as
(sequence item &key «:start i) 0) end)
It is important to nOle that if both &key and &rest arc given, then the list the &rest
variable is bound to is the same list from_which the keyworded arguments are extracted.
This is sometimes useful if the arguments are going to be passed en-mass to some other
function using apply, or perh4fps to reconstruct the original arguments to the function in
. order to signal an error.
&aux
Bindings specified with &aux arc for auxiliary variables: they have no correspondence to
the "argumcnts" givcn to the lambda expression. PIne only things which may follow &aux
MC:NILMAN:BIND 27
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-
NIL Manual 15 Lambd

Prcdic4Jtes 16 Nil. Mamml
4. Predicates
4.1 Type Predicates
4. J.I Type Specifiers
A type specifier is an expression which may be used to exprcs.~ a data-type constraint.
nil No object is of the type nit: nif is a subtype of aU types.
t All objects arc of the type 1. For· instctncc.
(make-array ·(10 10) :.element-type t)
m~tkcs an 10xl0 ~lrmy which can huld objects of any type.
tJt,c-name
This is the most common fhnn of type specifier; just a type name. filr insumcc number.
double-float. string. IJ1'('-llilmemay be .the name of 1 flavor defined with defflavor
(page 173). the name of a stnJcture defined by defstruct {page 125) (assuming defstruct
is not told to implement the stnlcturc in some other fashion). or one of the m,my NIL
types noted in various places in this document
(not type-specijiery
AU objects which are not of type type-specifier.
Carto !s! !s2 ... IS!?)
The intersection of the types corresponding to the given type spccifiers~
(or lsi Is) •.. tsn)
The union of the types corresponding to the given type sp~jfiers.
(member x) xl ... XIl)
This describes a type which is one of the objects xl, xl, ... xiz. Equality is defined by
eql (page 20).
(satisfiesjUnclion-name)
An object is a ttmember" of this type if junction-name returns a non-null value when
applied to it, otherwise it is not.
. There are some more complex fonns which are used variously as synonyms for, and
constraints on. more general types. For instance:
(integer low high)
An object is of this type if it is an integer between low and high. low and high may be
integers. in which case the boundary check is illclusive, lists of integers. in which case the
boundary check is exclusive. or the atom ., which signifies infinity of the appropriate
sign. Thus. (integer 0 .) is a type specifier for all non-negative integers. and (integer
(0) .) or (integer 1 .) for all positive integers.
(signed - byte size)
(unsigned - byte size)
An object is of these types if it can be r.cprcscnted in the appropriate fonn in twos-
MC:NILMAN:PRElJ 29
23-DEC-83
, .. ~ , - ~
-,.:,:c ".,~> .. ); ". }': ..', J'-. : : " ',' ~
,
,.... .' ,". . ~.
,

NIL Manua) 17 TYIK' Predicates
complement notation in a field of the specified size. (Without a hidden-bit convention.)
Thus. (signed -byte 3) is the same as (integer -4 3). ,1Ild (unsigned -byte 3) is the
same as (integer 0 7).
bit Either 0 or 1.
(array element-type dimensions)
An object is of this type if it is an array with "the same" clement type and dimensions as
those specified. dimellsions may be the symbol • (or not supplied). which matches an
array of any rank and dimensions. Otherwise. it should he a list: it then matches an
array \vhose rank is the length of the list. The clements of the list may be either the
symhol *. or a non-negative integer which is the size of the corresponding dimension.
For instance. the dimensions Jist (3 4 5) refers to a 3x4x5 array, ,md (3 • 5) an array
whose first dimension is 3., second is of any size. and third is 5.
There arc two different contexts the type specifier can be used in. and they affect the
interpretation of the eJemeIlJ-t)1Je. These arc
declaratioll
in which something is being declared to take on values of this ty)e (declarations
arc discussed in chapter 6). What the type specifier says is that the type is the
same as would be returned by make-array were it given an clement-type of
element-type and dimensions conforming to dimensions.
discrimination
which is really JUSt usc of the type specifier as a second argument to typep. In
t,;is ,,,:;e, the questk,n being dskeJ is w'hcthcf i,he ubjed tJ\.:illg h:~ico i~ uf e.xac/iy
this type.
These two "questions" arc different because of the way make-array (page 103) interprets
its element-type argument. which is fully discussed in section 12.2. page 104. Basically.
what you get from make-array is an array whose clement-type is the closest specialization
to the specified element-type which make-array can provide.
Finally. the elemelll-type can be *, which means any element type at all. Thus, (array t
dims) is a not a subtype of (array • dims). because the former only refers to arrays
which can hold clements of any type, whereas the latter includes bit arrays, string-char
arrays, etc.
(simple-array elemel1l-typ~ dimensions)
This is like (array element-type dimensions). but additionally states that the array has been
created without any "fancy options"; see chapter 12, page 103.
(vector elemenl-t}pe size)
This is equivalent to (array element-type (size».
MC:NILMAN:PRED 29
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Type Predicates 18 NIL Mcamwl
4.1.2 General Type Predicates
typep objecl &optional type-specifier
If only one argument is supplied. this is (somewhat) like MACl.ISP typep, and returns the
exact implementation type of object. In NIl.. this is usually something too specific to be
worth looking at
Otherwise. returns t jf object is of type type-specifier, nil otherwise. See thc description of
type specifiers. abovc.
sub typep (l1)l'-Spcc(fin'"' (l'l'l'-Spccijir,... 2
subtypep attempts lo dClcnnine if I)1J('-sp('cijier-r is a subtype of ~l·l'c-spl'(·ijier-2. It
returns two \'4tlues~ the sC(,(Jlld will he t if thc rchllion could h(' determined. nil if il could
not he. Thc first is t if the rehltion can be determined and 1J'1'c-.VJccilier-' is in filet a
subtype of 1)1U'-lPCCijicr-2. nil otherwisc.
In \,lL if the type spccifiers are atomic type names and Iype-spccijie,../ j'.: a subtype of
I),}}('-specilier-l. then subtypep will probably succeed in determining this. ~,I t),pc-spcdjie,..
/ is 1101 41 subtype of I)'pr-spcdjicr-2. then subtypep may fail to be able to detcmline the
relation. because it may not know that panicular supcrtypcs are mutually exclusive.
For instance.
(subtypep 'fixnum 'number) => {t. t}
(subtypep 'character 'number) => {nil! t}
(subtypep 'number 'fixnum) => {nil, t}
(subtypep '(satisfies fixnump) 'number) => {nil. nil}
4.1.3 Specific Type Predicates
null object
This returns t if object is nil. nil otherwise. Stylistically. null is used to test for object
being the· cmpty list, whereas not (page 28), which is functionalJy equivalent because of
the empty-listlboo)ean-faJse duality of nif, is used to test for boolean falseness. This is
why constructs of thc fonn
(i f (not (null x) 1 frob-non-nul/-x frob-null-x)
are so prcvalent.
symbo lp object
Returns t if object is a symbol, nil otherwise.
consp object
Returns t if object is a cons, nil otherwise. This is the same as (not (atom object».
11 stp. object
consp or nult
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NIL Manual
19
Type Predicates
f1xnump object
characterp object
These test for the exact types fixnum and character.
str1ng-char-p character
Tells if character is a character which may be stored in a string. 'Ibis wiJ] be a type of
sorts in COMMON LISP, such that a string is a vector with clements of type string -char.
Note that string-char-p requires its argument to be a character. as opposed to just any
object: it is not really a general type prcdicate~
In 'II., this is characters with bill' and fiJI/I of 0 (sec chapter 11).
str1ngp object
vectorp oNect
Tell if ubject is a string or vector respectively.
O~;(,CI 'string) and. (typep object 'vector).
These arc equivalent to doing (typep
numberp object
f10atp object
These are the same as (typep object 'number) and (typep object 'float) respectively.
closurep object
Tells if object is a closure.
The following are supported for MACUSP compatibility:
pa 1 rp object
lbis is synonymous with consp. Once upon a time. the name for cons in NIL was pair,
and the function pairp was installed in MAC1JSP. Now, NIL and COMMON US}> call a cons
a cons.
b1gp object
(typep object 'bignum)
11xp object
Equivalent to integerp. i.e.. (typep object 'integer). This name should be avoided
because of possible confusion with fixnump.
flonump object
This is the same as (typep object 'double-float). for historical reasons, not the same as
ffoatp. It is provided for MACLISP compatibility only.
MC:NlI.MAN:PRPD 29
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EqlWfilY Predicates 20 Nil. Manual
4.2 Equality Predicates
Note also null (page 18) and not (page 28). for testing for nil.
eq x y
'Ibis tens jf x and J' are the exact same opjcct. Implemcntationally, this is truc if x and y
arc the same "pointer". For instance.
(setq -foo-(con5 'a 'b» => (a. b)
(eq -foo•• foo*) => t
(setq *bar- (cons 'a 'b» => (a. b)
(eq -foo* -bar*) => nil
Philosophically. what this predic.lle S

NIL Manual 21 Equality Predicates
equalp x y
This is a more "general" version of equal. Numbers are considered to he equalp if they
are numerically equal; type conversion wil1 OCCllr if needed to pcrfonn the comparison
(see =. pagc 73). Charactcrs are compared with char-equal (page 95). so are considercd
equalp cven jf thcy differ in casco Conses arc equalp if their respective cars and cdrs
are equalp. Arrays arc equafp jf they have the same rank and dimensions. and if their
corrcsponding clemcnts are equalp: thus. a string will be equalp to a gcneral vector
containing equalp characters:
(equalp #(#\F #\0 #\0) "foO") => t
equalp. likc equal. is imp1cmcnled reclIrsi\cly so may dk' on circu1ar structures.
MC:NILMAN:PRED 29
23-DEC-83
, ,. ", ',' ,'" ,:" • O'" ' ',,', :, ,': ',' ,: . " ' , '
-, -
--' '".; .;-.. ' :~~'~~:-. "',~:'".' ---,.'., ~,:, -: ;': ,-, - " '..:- .', -, ' ,

Programming Constructs 22 NIL Manual
5. Progralnnling Constructs
The NIL special and top)evel fonns.
5.1 Compositions
progn {{onn}-
progn evaluates each of the fhnns~ and returns the value of the last. It is. therefore. a
way· (0 get multiple expressions in a position where only one is caUedfhr.
(progn) nil
(progn jiJnll) jiJnl1
and
( pro 9 n fo n,,·/ jiJnn-2 .•. jiJnl1-11 )
evaluates ,111 of the fontls. returning the result of the evaluation of [onn-n.
Back in the olden days of LISP. mc.my ~pecial foons only allowed a single expression
where we now allow multiple expressions to be cvaluatcd in sequence; for instrlflce. in the
consequent') of the cond special form (page 28). This often necessitated tJleexplicit lise
of the progn special fonn in such places. and is where the tenn implicil prugll. which
describes a situation where such multiple forms are allowed. comes from.
prog1 first-fonn {{onn}·
prog1 ~v:lln;ltC'C\ fir'i/-fnrm. (\nd s~ve~ tht:' v~'lJe: then it cvaluat~ an of t.~e other fcrm~.
but instcad of rcturning the value of the last like progn docs. it returns the value saved
from the the evaluation of jirst-[onll.
prog2 first-Jonn second-fonn (tOmt)­
This is entirely equivalent (0
( pro 9 n firsi-fonn (p r 0 9 1 second-fonn fonn. •• »
In other words, it evaluates all of the fonns in order, and returns the value (it saved) of
the second.
5.2 Definition Forms
5.2.1 Defining Functions
defun name lambda-list {declaration}- [documentatioll] {fOnn}-
Defines name as a function, equivalent to a lambda expression formed using the lambda
IisL declarations. and forms.
For MACLJSP-Compatibility, the following idiosyncratic syntaxes are recognized specially:
(I) If lambda-lisl is the atom macro, then this is assumed to be a MACI.lsp-style
macro definition. and is transfonned appropriately.
(2) If lambdwlisl is a non-nuH atom, then this is considered to be a MACLISP lexpr
definition. name will be defined as a function of a variable number of arguments,
MC: N II.M /\ N: pca NS 81
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:,::': ,":_:.:"0·;~;\. '.- .. -:,;:;>.t:~:;.~c~.,;

Nil. Manual 23 Dc·finilion Fonns
and the symhol lambda-list hound to that number. The functions arg and setarg
may then he used (compatibly with MACI.ISP) to access the arguments.
(3) If lambda-list is the atom fexpr. then this is assumed to be a MACLlsp-style fexpr
definition. and an attempt is made to turn it into a Nil, special fonn. Note. of
course. that due to evaluator semantics this will usually not work (caBs to. eval
will. for instance. utilize a new lexical contour).
In principle. name is a general function specifier ("function-spcc") as is done in LISP
MACIII'F IISP. However. these hm'c not been put into ~I1. yet. so one additional
idiosyncratic syntax (also MACI.ISP compatible) is recognized: lIalllC may be a list of the
form (namc I'ropl1amc). in which case the function is placed on the propn(]mc properly of
namc. That is. one can do something like
(defun (faa hack) (x y)
(list (* (sinh x) (cos y» (* (cosh x) (sin y»»
with the result that
{funcall. (get 'foo 'hack) x y)
will invoke a compiled function to perfonn that computation.
5.2.2 Defining l\lacros
A LISP macro differs from an ordinary function in that the code of the macro is run, not' to
obtain a value for the fonn. but rather to obtain a new fonn to be used in place of the original
form. 1n 'lSP. thiC\ iC\ nnt (innp thr(lneh ~ny stf!mz~ and miracu101..!s string-processing and
substitution. but by USP code itself: LISP program code is just LISP data. which can be
manipulated and constructed by ordinary LISP programs. When a macro call is encountered by a
USP compiler. the code for the macro is run then and there. during the compilation. to construct
the new fonn which must be compiled instead. For that reason. LISP macros. while general LISP
functions, should not depend on their dynamic environment (although if properly arranged they
may have global declarative or definitional information around).
defmacro name pattenl {declarations}* {documentation}- Yonn}*
This is the preferred way for macros to be defined. name is defined as a macro. When a
call to name is encountered by the interpreter or compiler, the list of arguments to name
(specifically, the cdr of the calling form) is matched against paltern; the fonns are then
evaluated in an environment where the variables specified by pallern are bound to the
components of the arguments which they match. and the resulting value is used in place
of the original fonn.
pallem is general1y a pattern of symbols and conses. but it may also have in it,
intennixed, &optional. & rest. and &body. (&body is treated just like &rest by
defmacro pattern matching. However, it is supposed to be an indication to a code
fonnatter (pretty-printer. or an editor) that the following forms are a "body" rather than
just a sequence of more arguments.) The following defines foo as a macro to be
synonymous with car:
(defmacro foo (x)
( 1 is t • car x»
In NIL. the &mumble keywords need not be "top-level" within the pattern:
MC:NILMAN:PCONS 81
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I xfinition Fonns 24
(defmacro with-output-to-string «var &optional string).
&body form)
... )
Especially useful fhr constnlcting code in the bodies of macros is the backquote reader
macro. section 20.1.1. page 216.
Eventually. defmacro will be extcnded to support these additional Jambda-list keywords:
&key kcyspecl keyspec2 ...
Pretty much like the ordinary lISC of &key in lmnhd,. lists (section 3.1. page 13).
&whole l'l.1riablc
Binds l'lIri41b/(' to the ma

NIL Manual 25 Binding and Assignment
5.2.4 Controlling Evaluation Time
Macros often need to return multiple fonns to be processed as if they all appeared
independently at lOplevel. For instance. defvar and its variants could all be trivially implemented
as macros (if they aren't already). In 1'11.. they may be returned within a progn special fonn.
For instance. a simplified defparameter, which did not handle documentation, could have- been
written like this:
(defmacro defparameter (variable value-form)
t(progn (proclaim '(special ,variable»
(setq .variable .value-form»)
proclaim and declarations are described in chapler 6. p,lge 41. The \1:\( 'liSP hack where the first
clement of the progn had to be the fllnn (quote compile) is not needed (but will work just fine).
This behaviour and the special casing only applies to toplevel fonns.
ev 81 -when kwd-list lfonn}"
This is as if each of the forms appe~red at topleve1. but were only there to be processed
at the times specified by kwd·/isl. The allowable keywords for kwd-list are
eval
When the eval-when fonn is evaluated by the interpreter.
load
When the forms of the eval-whenare loaded compiled (they will be treated as if
th~y were:- ~l?l?n at top!eve! by the compiler; c.g., defuns wi!! b~ cmnpH~d. ~tc.).
compile
The jonns will be evaluated immediately when processed by the compiler. Note
that eval-when keywords arc 1101 symbols in the keyword package (that is, you
don't type them in with a colon in front).
Note that for historical reasons, these "keywords" are only keywords in the general
sense-they are not symbols in the keyword package (typed in with a colon prefix).
5.3 Binding and Assignment
setq {variable value}-
setq changes the values of variables.
(setq a (f) b (g»
makes the value of a be the result of evaluating (t), then makes the value of b be the
result of evaluating (9). The value returned by setq is the last value stored/computed,
which in this case is what b now will evaluate to, and what (9) evaluated to.
The choice of whether to change the lexical or dynamic value of the variable which setq
makes is the same as that which would be made by the evaluator in evaluating the
variable; and if there is no binding of the variable. setq creates a global dynamic value
for it.
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Binding and ;\ssignment 26 Nil. Manued
psetq {variable value}-
psetq is syntactically like setQ. but it updates the variables in parallel. That is. an of the
values are computed. before any of the variables are side-effected. A common idiom
which uses this is
(psetq x y y x)
which exchanges the values of x and y. .
psetQ always returns nil.
let ({\'{lriab/e value}' {declaratiull}- {/bn,,}-
let evaluales all of the nilu('s. and then binds illJ of the l'ariablr ., to the corresponding
valllc~. ;\11 of the "alues arc cumputed betl)re any of the bindings are perf(lIlned.
(let «a (f». (b (g)))
funns. .. )
evalu3t.es (f) and (g), then binds a to the result from the evaluation of (fl and bto the
result of the eyaluation of (g). and then evaluates all of the forms: the value of the last
fimn is returned ,IS the value of the let.
Various other constructs in ~I1. accept a list of lists of variables and values syntactically
the same as that used by let. This is Wh,lt is meant by the tenn lel/isl.
In NIl.. let will accept in place of a variable. a pattern used for deslTUc/urillg. The
variables within the pattern arc bound to thc corresponding parte; of the value. This is
"imil~r to thp iJ'lf('rf.'l(,C' t(l d~strlJc!t!nng used by d~fmacro: see it. page :n. for mere
infonnation on this pattcm·directed deslfucturing.
Because COMMON US}> let is not defined to suppon destructuring. it· is recommended that,
if destructuring is used. it be hidden in a macro. This will make it both easier to read
(an tllC extra parentheses needed to use let with deslfucluring make it hard to read), and
also make it easier to change should let eventually be changed to 110/ support
destructuring (at which time there will be a primitive provided which docs). For instancc 9
the !"IL compiler defines the macro debind-args to destructure argument lists of fonns
being compiled:
(defmacro debind-args (arglist-pattern form &body body)
-{let «.arglist-pattern (cdr ,form») ,8body»
Eventually NIL will provide some special fonns and functions for getting at the
destructuring and argument· list matching functionality provided by defmacro.
let. ({(variable value)}' {dec/oralion}- {{onn}-
Syntactical1y, let. is similar to Jet. However. rather than binding the variables in parallel.
it binds them sequClllially. That is. when each value fonn is evaluated. the corresponding
variable is bound to that value, and the following values are evaluated in that
environment. For instance,
(1 et. « a jomlJ) (b fonn2»
compute}
first evaluates fonnl. and binds a to that value. Then. it evaluates jOnn2, and binds b
,to thaI value. Finally. it evaluates compute and returns that value as the value of the
let·.
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Nil" Manual 27 Binding and Assignment
5.3.1 DynamicaHy Binding Variable Variables
The routines in this section may be used to bind variables which are not known at codewriting
(or compile) time. They all bind the special (dynamic) value of the variable.
There are four variations on how the variables may be bound. Which is used is a matter of
which is best suited for the particular task at hand. Basically, the variations all involve how the
value is computed.
progv varlis, vallis, fonns ...
progv binds each of the ,"ariahles in \,o"'is/ to the corresponding "allies in rallis'. If there
arc too many values in ml/isl. the extras are ignored. If there are too Icw. then the
extra variables will he bound "unbound". P.ach of the forms is then evaluated in an
environment in which the variables arc so bound: they arc all bound dynamically.
progv is defined by (,OM~10N-I.ISP.
None of the following spechtl fmms are, however.
The following three spedaJ fonns an take an a-list as a specification of what variables to bind
to what values. The car of each entry in the a-list is the variable to be bound. I f the 'cdr is nil
(the entry has a length of 1). then the variable will be bound "unbound". Otherwise. tJle cadr
(110/ the cdr) of the entry tens what value the variable should be bound to: the exact
interpretation varies with the special fonn in use. In all cases. the bindings are pcrfonned
sequentially: each variable is bound to its value before the value for the next variable to be
bound is detcnnined.
progw a-IiSl funns ...
The second clement of each entry in a-list is a fonn to eval to get the value to bind the
variable to.
progwq a-list fonns .••
This is son of a trivial special-case of progw. The second clement of each entry in a-lis/
is the actual value to bind the variable to; no evaluation is perfonned.
progw1 a-list forms ...
This junction may lIot yet be ill the existing NIL.
This is a variant of progw more in keeping with a LISP implementation in which things
get compiled. The second element of each entry in a-list is a function to be called on no
arguments to detennine the value to bind the variable to. This is much more practical
than progw because it can eliminate a lot of interpreter overhead.
The typical use of these special fonns is to provide a dynamic environment. the specification
"of which may be augmented modularly, and hence might not be totally known to the writer of
the code which pcrfonns the binding. progw and its variants are usually more convenient for this
purpose than progv. because the specification of the environment is in a single datastructure.
which might be kept around as the value of a variable. Note however that progw. progwQ. and
progwf are /lui defined by COMMO:"'-liSP. progw is defined by LISP MA(,II(~E LISP, but progwQ
and progwf are not.
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Conditionals 28 Nil. Manued
5.4 Conditionals
1 f predicate cOllsequel1l [else/omlJ
not x
if evaluates predicate. If the result is not false (i.e.. nO( nil). then the result of the if is
the rcsult of evaluating cOlJsequent. Otherwisc. jf· else/onn is specified. the result of thc if
is the result ofevaJuating else/onn. otherwise nil.
not is used )ogical1y (0 invert the scnsc. of a predicatc. That is. it is byconvCnlion used
to test for the object representing boo/ran jill.')£'. Because of the emply-list/booJean-faJse
duality of the symhol nit. iris functionally equhHlcnt to nuft (page 18). which logically
checks fbr the CIIII'I)' /isl which is represented by thc type named nult Thus. one ottcn
sees c()nstruct~ of the thml
( i f (n 0 t (n u 1·1 1» ('()f1scqU(,111 r/sejiJn1l)
because nuff is used to check for empty-listness (fbr instance. being m the end of an
iteraliun down a list). and the not is used to invert the sense. so that the cOllsequcllt will
be nm if there is in facl something left to the list l.
cond {(prctiicllir {collsequent}-»-
GenemJ historical condo Each predicalr to the cond is evaluated. in order. If the result
of an evaluation is false. then the cond evaluates the corresponding consequents in that
"clausc", returning as its value the vatuc(s) of the last one. unless there were no
consequents. in which case the value of the cond is the value of the predicl1le evaluation.
\ ..... It... \,....~. ,
I"",",. 1 .. 1 ,.1\
(p2 c2)
(t e»
is equivalent to
( if pI cl
(if p2 cl e»
however cond al10ws multiple consequents. and also may more clearly show the selection
by clearly listing the sequentially processed tests.
If a11 of the predicates are false. then cond returns nil.
when predicale-/onn {consequent-form}­
(when predicate-form
consequent-J
consequent-2
cOllsequent-n)
==>
(cond (predicate-form
consequent-J
consequent-]
cOl1scquelll-n) )
If predicQte-/onn evaluates non-nuU. then the cOllsequl'llt-jOnns are eva1uated in order and
the valuc(s) of the last one returned as the value of the when fonn: otherwise. the when
fonn returns nit
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NIL Manual
29 Conditionals
un les s predicate-fonn {collsequelll-jhml}·
( un 1 e s s predicate-fonn
consequent-I
cOllsequent-2
consequent-n)
==>
(when (not predicate-Jon,,)
c0l1sequclII-1
COIlSl'quCllt-2
c0l1sequel1t-11 )
==>
(cond « not predicate)
consequelll-I
. cOllsequelll-2
cotlsequent-n) )
and {tOnn}·
Evaluates each fonn. and if any returns nil. and immediately returns nil without
evaluating any subsequent forms; otherwise, the result of the and is the value(s) of the
last foml. (and) = > t.
or {fonn}·
Evaluates each fonl1, and if one returns a non-null result. that value is returned by or .
without evaluating any of the following forms. (or) = > nil.
or is supposed to return exactly one value, no matter how many were produced by the
evaluation of a form. except for the last fonl1 which is evaluated tail-recursively (with
respect to multiple value propagation). It doesn't currently behave Quite this way.
case keJfonn {(({key·}) {consequent}'}*
A dispatch fonn utilizing the eql predicate. In general,
(case keyform
( (key-I-I key-I-2 .•. ) fonn-I-I form-I-2 .•• )
( (key-2-1 key-2-2 .•. ) form-2-1 form-2-2 ••• )
... )
is essentially the same as
(let «tern keyfonn»
{cond « or (eql tern 'key-I-/) (eql tern 'kerl-2 ) .•. )
/onn-i-I foml-I-] .•. )
«or (eql tern 'key-]-/) (eql tern 'key-]-2) .•. )
jOnn-2-1 /onn-2-2)
... ) )
Since the keys are constant. however. it is possible for the compiler to detcnnine the
cheapest way to perform the comparisons; see eql, page 20. In fact. if there are a
moderate number of fixnum keys in a small range. the NIL compiler may use the VAX
CAS E instruction to perform the dispatching.
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Function I nvoc,ltion 30 NIL Manual
In place of a list of keys. one may usc a single atomic key. Also. the symbols t and
otherwise are special-cased and cause thaI "clause" to always be selected; no subsequent
clauses will he examined. For example,
(case (. 2 2) .
(1 'one)
(2 'two)
(3 'three)
(t 'many»
=> many
Nole that if one needs to lise nil. t. or otherwise as keys. they should he enclosed in a
list: otherwise. nil wi11 be interpreted 4lS an empty list of keys. and t and otherwise as
signifying the "ot.herwise" clause.
This function is what selectq thought it would once be. and may be lIsed in place of
MACI.IS., caseq.
typecase ()l~;r(" {(/)1Jr-sprcijirr {limn},}--
typeease examines each of its "clauses" in turn. If object is of the type specified by that
I),pr-spcc{ficr (sec typep. page 18). then the ji,nlls in that clause arc e"alu4tted. and the
value of the last fonn is returned by typecase. If a 1)1JC-Spccijicr is one of the symbols t
or otherwise. then that clause will always be selected. and all subsequent clauses will be
ignored.
factoring out operations needed filf more th~lO oJleof the checks. The ;\IJ typecase docs
not yet do any clever pointer';'lype dispatch, however.
Remember that each "key" is a type specifier: it need not he just a type name. and it is
definitely not a list of type names. To test for more than one type in one key, usc (or
type! type) ... ).
5.5 Function Invocation
Often the function one desires to can is not constant: for instance. it may have been passed
in as an argument (like the second argument to sort. page 55. or as a :test key worded argument
to member. page 61. or something obtained from a propeny list. hash table. or association .list).
NIL does not suppon the old "functional variable" interpretation of a functional fonn; that is, in
a fonn like (foo x y). the function called is never obtained from the value of a variable foo.
Instead. because the "name space" for functions and variables is completely distinct, so special
functions are provided for invoking functions which are obtained by "normal" evaluation.
tunea 11 fone/ion &rest orgs
funeaU caUs junctioll on aU of the arguments in orgs. It is 1101 a special fonn; the
junctiull is evaluated in the regular filshion. and that value should be a function. For
instance. sort (page 55). which could be defined something like
(defun sort (sequence pred &k~y key) ... )
could invoke its pred argument with something like
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NIL Manual 31 Iteration Constructs
(funcall pred (elt sequence i) (elt sequence j»
apply fullction &rcst args
apply is somewhat like funcall. but the last of the args is a list of the remaining
arguments to invoke /unctioll on. That is~ if apply is called like
( app 1 y jil af a2 .•• all list)
then III will be invoked like
(funcall In aJ a2 .•. all el e2 ... em)
where eJ c2 ... em are the clements of list.
Often. the last argument tu apply is a list which is thc \'aluc of an &rest \ariab}e. 1 n
~IL. this Jist may instead be a simple vector (it must be simple). as might be obtained by
use of &restv instead of &rest.
.Note that the ~1ACLISP apply function only acceptli two arguments. if you don't count the
optional third argument which is an evaluation environment.
lexpr-funcal1 jUllction & rest args
Old name for what is now done hy apply. lexpr-funcall. unlike apply, is compatible
with MACUSP.
5.6 Iteration Constructs
5.6.1 Mapping Functions
mapc junction list &rest more-lists
map 1 jullction list &rest more-lists
mapcar jullction list &rcst more-lists
map 11 s t junction lisl &rest more-lists
mapcan function list &rest more-lists
mapcon junction list &rest more-Iisls
These arc the standard complement of USP mapping functions. which iterate down all of
the lists in parallel. They accumulate results in three different ways, and apply jUnction in
two different ways. In all cases, if more than one list is supplied, they are stepped in
parallel and the iteration tenninates when the end of the shortest one is reach.
mapc and mapl each returns its first argument as its· value; that is, they are typically for
effect. mapc applies IUllctfgn to the cars of successive sublists, that is, to the elements of
the lists. whereas mapl applies Iunction to the sublists themselves. Thus,
(mapc #'print '(a be»
prints
a
b
e
whereas
(mapl #'print 9(a be»
prints
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Ill'ration Constructs
32 Nil. Manuul
(a b c)
(b c)
(c)
Both rcturn lisi. their first argument. Note that the function is not called on the nun list,
evcn though thm might be thought of as a sublist. Random example where the return
value is useful:
(mapl "(lambda (subl)
(rplacd subl (delete (car subl) (cdr subl»»
some-list)
eliminatcs (dcstnlctively) all duplicate element~ from some-list.
mapl is what used tu be called map in MACI.lSI).·
function (p4t£e 54).
map is now a generic sequence
mapcar and mapfist each returns a list of thercsull~ uf appJying JUl1eliol1 to tJlcir
successive arguments: for map car. as with mapc. the arguments are the clements ofthc
lists. and for maplist. as with mapf. they ar~ the sllblists themselves. For eXilmple:
(mapcar #'(lambda (x y) (plus x y»
• (1 2 3) • (9 10. 11»
=> (10 1214)
That could have been. written as
(mapcar #'plus ... )
mapcan :!nd mapccn "$p!ic~ tog~th~r" the results of applying ju;;Nivn to its succeSSive
arguments. using (essentially) nconc. One common usc of mapcan is to mapcar
conditionally:
(mapcan #'(lambda (x) (and (pred x) (list (fx»»
smne--Iist)
is kind of like doing (mapcar # '/ some-list) having first deleted those elements which do
not satisfy pred.
Because of the constrained nature of the iteration, mapcar, maplist. mapcan, and
mapcon probably generate better code than you (oreveD something like the loop macro)
could write for generating the return value.
5.6.2 Other Iteration Forms
dot 1mes (var count [end/onn]) {dec/aration}- {tag I fonn}-
var is stepped from 0 (inclusive) to the value of count (exclusive); for each value, each of
the /onns is evaluated. When the iteration tenninates. the value of end/onn is returned.
The "body" of dotimes is a "tagbody" body (sec tagbody). Atomic tags may be inscncd
among the forms and jumped to with go (page 34), to produce strange and wondrous
unstructured code.
AdditionaHy. dotimes establishes an implicit block named nil around the dotimes fonn
(sec block): one may thus use return (or return-from with a block nrune of nil) to exit
and return a vaJuc(s) from the dotimes. without running exit/ann. block and tagbody
are described in section 5.6.3, page 34.
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NIL Manual 33 Iteration Constructs
dolist (var list [cndfimn]) {declaration}* {tag I jiJnn}*
Similar to dotimes. hut steps var through the clements of list. the way mapc (page 31)
d\)es.
dovector (var vCClor) {declaralion)· {tag I fonn)·
Similar to dolist. but for vectors. dovector will work on any type of vector: its' name
and existence dates from the early days of NIL when all vectors were simple vectors. If
vcctor is going to be of some known specialized type. one might be able to get better
code hy llscing one of the specialized loop constnu:L4iavailable in NIl.. as discussed in
section 17.7.1.2. page 163.
do ({var [inil [s/cp]])' {cndlcst {el1lljiJnl1}*) {declaraliol1}· {lag I form}·
do is a more general iteration constnlCt. The specified variables arc bound in parallel (as
by let. page 26) to the values of the corresponding initial values. These are their values
,for the first iteration. For all subsequent iterations. the variables which have step forms
specified are all set in parallel to the values of those step forms. (That is. the values of
all of the step forms are computed b~fore allY of the assignments have been made.)
On each iteration. elldlest is evaluated. If the result is not nil. then the iteration
terminates and e\'alu~tes the elld/onus as an implicit progn (returning nil if there arc no
elldfonns). Otherwise, the "body" of the do is interpreted as by tagbody (page 34).
Thus.
( do ( ... ) (n i 1) tagbody ... )
( do (...) (t ... ) tag body . . . )
will never get around to interpreting the forms in tagbody.
do establishes an implicit block named nil around the entire do fonn: see section 5.6.3.
page 34.
As a special hack for MACLISP code. if endrest is not specified (and hence no endfonus
could be specified). then the body of the do is interpreted exactly once. and nil returned;
that is. the do should have been written as prog (page 35), except that MACLISP prog
docs not accept initial values for the variables.
do.
The MACLISP "old style do" is also supponcd in NIL. This takes the fonn
( do var inil step elldtest tagbody ••• )
and is equivalent to
(do « var init step» (endtest)
tagbody • .. )
New code should not use this fonnat.
Specialfonn
({(var [illil [step]])} -> {endtest {endfoml) -> {declaration)· {tag I fonn}·
Ihis is like do, except that the variables are bound to their initial values sequentially (like
let- (page 26) rather than Jet). and the steps are also performed sequentially (like setq
rather than psetq).
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Iteration Constructs 34 NIL Manual
See "Iso the loop macro, page 144. loop is a "programmahle iteration facility". which allows
one to combine various sorts of iterations (such as those provided by dotimes and dovector) with
vilrious sorts of result accumuhttion (such as those provided by mapcar. mapcan. every. some.
and other things such as summing and counting). Because it is complicated. it is documented
fully in Ch4tptcr 17. page 144. An earlier version of that chapter appeared as [51. which is
expected to be re.vised· similarly.
5.6.3 Block and Tagbody
block Clnd tagbody together implement the flow-of-control functionality pf()\'idcd hy standard
prog. prog could have been implcmcnted as a milCro in terms uf these and let. and in filet is
descrihed in that filshion by COMMON LISP.
block nome {declaralion}- ljorm}*
block· evaluates the jiJrms. If a lcxicaJly apparent return-from is evaluated with a tag of
lIome (or l1ame is nil arid a return is evaluated). then the vaJue(s) of the form given to
return or return-from arc returned as the \"alue of the block form. Otherwise'. the block
filrm returns the valuc(s)uf the evalumion of the lClst fonll.
Note that the argument to return or return-from is evaluated in the environment in
which it occurs, 1101 the environment where the block was established.
return fonn
Evaluates jbnl1 , and returns the value(s) it returns from the nearest lexic.llly apparent
block with a name of nil. Many special forms implicitly establish blocks named nil. such
as prog. do. do list. dotimes, dovector, and (usually) loop.
Note that this differs subtly from LISP MACIIINFl.JSP. In LlSI' MA(,IU~F. I.JSP. return
returns from the innermost prog (Le.. block) which is 1101 named t. In NIL (and COMMON
LISP), a return to a block name of nil only matches a block name of nil, and the block
name t is not distinguished in any way.
return-from name form
Evaluates fonn, and returns the value(s) it returns from the nearest lexically apparent
block with a name of name. name is not evaluated.
tagbody {tag J form}-
The body of a tagbody is examined sequentially. If a fonn is atomic. then it is a tag and
is ignored, otherwise it is evaluated. If during the evaluation a lexica11y apparent call to
go is evaluated with an argument of one of the tags. then control is returned to that
point within the tagbody fonn. which resumes its interpretation. If the interpretation
reaches the end of the tagbody. the result is nit
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NIL Manual 35 Non-Locall-"hl\\ of Control
It is important to note that the name matching of block/return-from and tagbody/go is
lexical. For instance.
(defun f (x)
(block foobar
(g #'(lambda (x) (return-from foobar x» x»)
(defun 9 (fn x)
(list (block foobar
(funcall fn x»»
(f 'faa) => faa
not (faa). The 7\11_ compiler cannot handle this example. however. Also. the named hlock only
has l~rllall1i(' e.rlclIl: if an attempt is made to return (0 a lexically apparent block construct which
has been exited. the interpreter will complain.
prog I'or/ist {dcdaralion)* {lag I form}*
_Swndard prog. l'arlisl may be a list of variables. or a list of lists of variables and their
initial values. They will be bound in parallel. prog can be built from the above
primitives:
( 1 e t varUs!
Ihe dec/a rations
(block nil
(tagbody the lags alldfonlls) ) )
For compatibility with LISP MACHINE LISP. if the first "argument" to prog is a non-null
"tuill. then th~t is uscd as thc jjam~ lif the blo~k.. wiih tlic \lal ii!)l ruiiuwiJJ~.
prog. \Iar/ist {declaratioll}* {lag I Jon,,}*
Like prog. but binds the variables sequentially rather than in parallel. i.e.. like using let.
(page 26) rather than let.
5.7 N on-Local Flow of Control
catch tag {{ann}*
COMMON USP catch. lag is evaluated and the result saved. Then. if during the
evaluation of the fonus. if a throw to that tag (as tested for by eq) occurs, the catch
fonn so named will return the values given to the throw. The tag so named has dynamic
extent.
The tag to catch is allowed to be any LISP object. This means that one can generate a
guaranteed unique tag by (for instance) (ncons nil). or by using a datastructure which is
somehow associated with the control point of the catch. This is. in fact. how the NIL
interpreter implements the block and tag body constructs; it uses the datastructures in
which it stores its control-flow infonn~ltion as tags to catch.
Note that this is incompatible with the standard MACI.ISP catch function documented in
the 1974 manual ([9]). However. PDPIO MACUSP has been bitching and moaning about
use of catch for some year or more now. advising the use of .catch instead (which is
equivalent to NIL's catch).
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Multiple Values 36 Nil. Manual
throw lag ibnn
Itlg and ji>nl1 are evaluated. Control is returned from the nearest catch established with a
tag eq to the value of tag. and that catch then returns all the values produced by fonn.
special form because of mUltiple value passb.lck. of course that doesn't work reliably yet.. ..
Note that this is incompatible with the old-fashioned MACI.lSP throw function. However,
in PDPlO MACI.JSP throw has been out of vogue for some time, supplanted by * throw.
which has syntax and semantics identical to this throw. and which is supported in 1'11 .•
unw1nd-protectpmtcC(('ti-.l'onll {dCdllup-jonn)*
prolcclcd-jimll is eyalmlted. and the result returned. Upon exi( the ('/eclllup-/CJnIlS arc
evaluated. No matter how the exit is achieved (throw. error. whatever).
In principle. unwind-prote~t returns wh~ltever extra values protected-jon" did. In the
current 'implementation. this cannot be guaranteed bccnusc no state is saved around the
evaluation of the c/l'lIIlUp-/onlls.
*catch tag {lbnll}*
Old name fi1r what is now catch. Wi1l be supported ~md identical to what catch is now
indefinitely. for the sake of MACLISP programs. which use this name with identical syntax.
(Note however that MACLISP catch allows lag to be a list of tags. which means it can't be
just any object.)
*throw tag jonn
Old name for what is now throw. Will be supponed and identical to wheat throw is now
indefinitely. for the sake of MAOJSP programs. which use this name with identical syntax.
This seems to be an ordin

-
NIL Manual 37 Multiple Values
val ues -11 s t list
Returns as multiple values all the clements of list.
val ues -vector veclOr
Because ~Il. makes such great usc of vectors. this is provided also; it returns a11 the
elements of vector as multiple values.
For example. in Nil. values is defined by
{defun values (&restv vee)
(values-vector vee»
Of course. the ~ll compiler will open-compile a caB to values.
mul t 1p 1 e-val ue variables values-foml
The variables in variables. which must be a list of variables. are set to the corresponding
!11U1liplc values returned by the evaluation of values-funn. Extra values are ignored: if too
few values are returned. the extra variables are set to nil.
multiple-value always returns exactly' one value. the value of the first value returned by
,'alues-fun1l (or nil if none were returned).
In NIL. as in USP MACHINE USP. one may use nil in place of a variable to cause the
corresponding value to be ignored. This is specifically disallowed by COMMON l.ISP. and
should not be used. The preferred way to handle this uses multiple-value-bind, below.
The name of this will be changed to multipte-value-setq by COMMON LlSP ...
mul t 1 ple-val ue-b1 nd variables values-fonn {declaration}* {{onn}*
Somewhat like multiple-value. except the variables in variables are bound to the values
produced by values-form. and each of the fonns evaluated in that environment.
Note that. although in NIL nil may be used as a placeholder in variables for a value
which will not be used, it may not in COMMON LISP. The preferred way to ignore a
value is to use a name for it, and deClare that name to be ignored; for instance.
(multiple-value-bind (quo rem) (%bignum-quotient-norm x y)
{declare (ignore quo»
(hack-about-with rem»
This additionally provides the benefit of having the value "documented" by vinue of
being associated with a named variable.
mult1ple-value-l1st jOnn
fonn is evaluated. and all of the values it produces are returned as a list. For example:
(multiple-value-list (values 1 2» => (1 2)
(multiple-value-list (values» => nil
mult1ple-value-progl first-fon" {fOnn}*
.This is likc progl (page 22). but returns all of the values produced by the evaluation of
firsl-jonn. progl is supposed to return only the first value, never the other values;
however. in the current multiple value implementation NIL uses, this cannot be depcnded
on.
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Generalized Variables 38 NIL Manual
5.9 (.eneralizcd Variables
S 8 t f {pI lice value} ...
setf is sort of a generalized setQ. Essenti(ll1y. a setf fonn expands into the code needed
to store each value into each plac(,. For example. just as
(setq x 3)
stores 3 intox.
(set' (car 1) 5)
stures 5 inw the car of the vaJue of J. As with setq. multiple p141ce/value pairs ,Ire
handled sequentially.
setf always returns the hlst v,due stored.
setf works on variahles. aU dcfincd car/cdr functions. array and scquence accessing
functions (aref. elt. vref. char. bit). get. various attribute accessors (symbol-plist..
symbol-value. symbol-function. etc.). and all accessors defined by either defstruct or
defffavor. In fact. it is the canonical (and the only fonnally defined) way to modify slots
of structures defined with defstruct. It also operates on a number of low-level NIL
primitives. including nibble. get-a-byte. and get-a-byte-2c.
setf also operatcs on certain other fonns whose "inversions" are not strictly side-effecting,
by pcrfonning the setf on an argument of the function (which must be valid as a place to
setf). Thesc include Idb and load;..byte. For instance, the side-cffect perfonncd by
{~ptf (lt1h hyflJspec place) ."al}
is the samc as
(set f place ( dpb \Ial bYlespcc place»
although· the return value should be different.
The set' mcthodology is even more helpful when the logical operation being perfonncd on
the place is "read-modify-writc". This means that the place needs to only be specified once in the
form.
As of this writin& the COM~ON LISP compatible setf has not yet been insta11ed in NIL, so
not all of the following macros may be in the NIL when it is released. This pertains to incf,
decf, shiftt, and rotatef. and anything having to do with how one might define such a macro.
setf. push. and pop have been in NIL for some time already.
pus h item place
Approximately
(set f place (cons item place»
except that order of evaluation is preserved, and the forms of place are evaluated only
once.
pop place
Approximately
(p rag 1 (car place) (setf place (cdr place»
but the fonns in place are evaluated only oncc. In otherwords, pop treats the contents of
place as a list stack~ it returns the top of the stack and pops it
MC:NILMAN;PCONS 81
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NIl. Manual
39
Property I -ists
1 nct placc &optional (drlta I)
Sets placc to plaer plus della.
dect place &optional (della I)
Sets plac(' to place minus delta.
shittf place! place) ... placell fonn
( s h i f t f place jbnl1)
is just like using setf.
(shi ftf place!· place) /i,nl1)
stores the valuc of placel into pluce!. and then the value of form into place2.
rotatet placel placc) ... placcll
rotatef "roUltes" the value of the places. '111e v,llue of place} is stored into placc/.
place] into place) etc., and placcl into placen. all in parallel.
5.10 Property Lists
A properly list is a list of even length. of alternating indicators and values. 'Illis is. of course.
the same datastructure which is the property list of a symbol. Note that this is not the same as a
disembodicd property list. which has odd length. COMMO!' LISP has generalized the property list
mechanism so that is attached neither specifically to symbols or disembodied property lists, but
rather interfaces to generalized variables.
Note: as of this writing. the CO\1MON l.ISP compatible setf. on which both remf and setf on
getf are dependent. has not been installed in NIL. As a result. there is a chance they might not
appear in this release.
gett place indicator &optionat default
getf fetches the value under the indicator indicator from the property list which place
evaluates to. If no such indicator exists, then default is returned. The standard MACLISP
get function could have been written as
(defun get (x indicator)
(typecase x
(symbol (getf (symbol-plist x) indicator»
(cons (getf (cdr x) indicator»
(t error»)
It is not really necessary for place to actually be a generalized variable. However, getf
may be used with setf (and all such similar constructs). in which case place obviously
must be such a thing. MACLISP putprop could have been written as
(defun putprop (x value indicator)
(typecase x
(symbol (setf (getf (symbol-plist x) indicator) value»
(cons (setf (getf (cdr x) indicator) value»
(t error»)
MC:NILMAN:PCONS 81
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- --
" '",', i" , "" ,:;.~:>;~.({~/;,: • ' , " '

.Jo _ • .... ' _ ~
Propeny loists 40 NIL Manual
'111(' utility of getf is that it may be used to manipulate "property 1isl~" stored in p14lCCS
other lhan symbols or the cdr of a cons. One might. fi)r instance. define a structure
with defstruct (page 125) which has one SIOl used to hoJda property list:
(defstruct (frobozz :named :conc-name)
initial-data
plist
(hyperspace~shift-co~nt O})
Then. items in the "property list" may be accessed by
( ge t f (f robozz-p 1 is t /robozz) illdi('i1Ior)
and set by
(set f (get f (frobozz-p 1 is t /mb()zz) iJllJictltor) Ilafue)
One may also do such things as
(incf (getf (frobozz-plist jrobozz) indicator»
to increment a value stored on tlle propcnyJisL
remf plac£' indicator
remf removes an indicator/value pair from the property list in place. In order to do so.
place must be a generalized variable usable with self remf returns nil if there was no
such pair for indicator, t otherwise.
get-propert 1es place names
get-properties allows one to search for a set of properties, It looks down the property
list in place: when an indicator is found which· is in the list names, then it returns three
Vu!uC3: u'Jc ·.."luc under that IndkaLui. iIi\:: indk'ilUi. and th~ suhIi~i uf i.h~ 1.IIUV\:1 i.y ii~i.
beginning with the indicalOf. (Thu~ the car of that sublist is the indicator. and the cadr
the value. This last value is what is returned by the MACLlSP get I function. page 69.) ]f
none of the indicators specified in names are found, then al1 three values g~t-properties
returns arc nil.
Not only can get - properties be used for searching for more than one indicator at once,
but the third value returned can be fed back to get-properties to continue searching
from that (or some later) point in the propeny list
Note also the property-list function get (page 65) and remprop (page 65).
MC:NIL~1AN:PCONS 81
23-DEC-83
" ,
',-~", :" _ " r, ::.. -.' ' -', ::, _" "~,," ,-, "'" .-'::' .", :: ,';..:",,: ':;, ,,,,., ,', ,",;:: " • -~' "'~'"
, .

NIL Manual 41 I )eclarations
6. Declarations
In LISP. there is only one declaration that affects program semantics (and is thus the only one
needed to make tJlem run correctly): the special declaration. All other declarations are for the
purpose of providing extra information abollt the program-this infonnation may be for the
compiler. for a code analyzer, or just as documentation for humans. The assertions made by
declarations may be tested by the l.ISJ> interpreter or compiler in order to find program errors,
and may be used to direct compilation strategies, so incorrect declarulions are illegal and may
cause erroneous results.
6.1 Local Declarations
The normal declaration mechanism associates the declaration information with a particular
context established by some special form or construct. This is what happens with a lambdaexpression.
for instance. which is "described" as
«(lambda lambda-list {declaration}. {jbn,,}.)
{lonn}. )
A dec/aration is either a fonn
(dec 1 are {dec/-spec..})
or a form which is a macro call which expands into such a declare form. Declarations are
handled specially by the forms they are within; it is an error for them to occur in other contexts.
even though this may not be detected. The various special forms which accept declarations show
"'w'here thGSC dcduiutiGns muy 4ippcar in their descriptions in this mam.i.iL Typkally, this is just
preceding any "body" forms. as in the above examples. A dec/-spec is a list. the car of which
must be a symbol which is recognized as naming some declaration; the possible symbols, and
what they mean. are shown a bit below.
Individual declarations fall into two categories: those which affect variable bindings, and those
which do not. Those which do~ associate with bindings perfonned by the special construct they
are associated with. For instance, both
(lambda (a b c) (declare (type long-float e» .•. )
(let «a (f})(b (g» (c (h»)
(declare (type long-float c»
... )
say that the variable c is being bound to something of type long -float, and that that particular
"instantiation" of c will always have a long-float as its value. The declaration in effect "attaches"
to the binding of the variable; only that particular binding is affected. The declaration in
(let «x (f»)
(declare (type x Single-float»
(let «x (cons x y») ••• }
... }
only affects the outer binding of x, and makes no statement about the inner binding.
declaration in
The
MC:NILMAN;DCLS 31
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~~ - . . . .....

Lo(al I )cciClfations 42 NIL Manual
(let «x (f»)
(declare (type simple-vector v»
· .. )
is in error. because there is no variable v bcing bound in the construct the declare is associated
with. let.
The other c~Jteg()ry of declaration is thepervasi\'t' declaraliOfl. which does not· associate with
variable bindings. These have lexical scope. delimited by the form the declaration occurs in. This
sort of de clara lion is in effcct for (111 parts of the spcciul lbnn: this indudcssuch things as thnns
which arc evaluated to obtain values for variables being hound. even if those forms arc not
strictly part of the ttbody" of the spccial «lnn. For inSi«Ulce. the optimize dccliJration in
(let «x (r») -
(declare (type x single-float) (optimize (speed 3»)
(let «x (eons x y»))
(mapc "(lambda (z) ... ) x)
· .. )
· .. )
~s ttin effect" everywhere within the outer let. unless it were to be locally shadowed by another
·.>ptimize declaration hidden in one of the fonns represented by the elipses. The fonn (f) to
which the x in the outer let is being bound. is affected by that declaration. On the other han

NIL Manual 43 I.ocal I )ec larations
6.1.1 The Special Declaration
(special va,../ va,..] '"
va,../l)
The special declaration differs from all other declarations in two ways:
• It is the only declaration which affects program semantics. and
• it is the only declaration which can both "attach to" variable bindings. and also be a
pervasive declaration.
This duality is partly for convenience. but also follows from what this declaration docs.
For those variables in the special declaration which are being bound hy the special form the
declaration is associated with. for instance x in
(let «x (f»)
(declare (special.x y»
fonus. .. )
the declaration is an immediale. or variable-binding declaration. It says that the special value of
x should be bound. so that x has dynamic rather than lexical scope. As a consequence of this.
unshadowed references to x within the forms. will refer to the special value of x-the one it was
bound to. which is no doubt what is desired. This docs not affect bindings which arc not so
declared: in
(let «x «f»)
(declare (special x y»
( 1 e t « x (g») ; x number 3
. .. x ... ) ; x number 4
... )
the inner binding of x is a lexical. rather than special. binding. because there is no special
declaration for it. This binding shadows the outer (special) binding of x. with the result that
reference to x within that inner let refers to the lexical value. which gives what (9) evaluated to.
This. then. is all really the same as how the type declaratitlO associated. as was described above.
If. however. there are variables being declared special for which there no bindings. then the
special declaration for them is a pervasive declaration, which affects their reference (it will stin not
affect inner bindings). For instance. in both
and
(let «x (f»)
(declare (special x y»
• .. y ..• )
(let «x (f»)
(declare (special x y»
(let «x (9»)
• •• x •••
. ~. y ••. »
the reference to y amidst the elipses is a special reference. due to the speCial declaration for y.
Note that by contrast the reference to x between elipses is lexical because of the shadowing effect
of that inner lexical binding.
The example function find-all-leaves from chapter 3. on page 12 (q.v.), can be rewritten as
~IC:NILM"N;DCLS 31
23-DEC-83

Local Declarations 44
NIL Manua1
(defun find-all-1eaves (tree)
( 1 e t «. 1 e a v e s • nil» ; Empty set ofleaves
(declare (special .leaves.»
(fi nd-a 11-1 eaves-l tree) ; Grovel over the tree
.leaves-
;And return the leaves found
} }
(defun find-all-leaves-l (tree)
(declare (special .leaves-»
(cond «atom tree)
(cond «not (memq tree .leaves-})
(setq .leaves- (cons tree .leaves-»}»
(t (find-all-leaves-l (car tree»
(find~all-leaves-l (cdr tree»}»
to demonstrate the common uses· (If the speciat declaration. The declaration in find - all -leaves is
an immediate declaration; it causes -leaves. to be dynamically bound. In find-aU-leaves-1. it
is a pervasive declaration which says that the references to .Ieaves. within that function are
references to the special value of -leaves.. It" hilppens that in find-all-leaves-1. both the
interpreter and compiler would figure out that the references to .Ieaves. would have to be
speciaJ references because they arc "free" references (there is no lexically apparent binding).
however the compiler would issue a warning about this. So. that declaration serves to teU the
compiler, the interpreter. and a reader of the code, that the references to .Ieaves. in find-aUtrees
-1 are deliberately special.
6.1.2 Declarations Affecting Variable Bindings
Here arc the other declarations NIL accepts which associate with variables. being bound. It is
an error for a variable to be specified in one of them. when it is not being bound by the
construct the declaration is, associated with.
(i gnore VQ,../ va,...2 ••• va,..n)
This says that the specified variables. although bound by the associated construct, are not actually
used. Its purpose is to tell the NIL compiler that you are aware that you wiU not ever reference
the values of those variables; otherwise, it might warn you that the variable is never referenced.
One common use for this declaration . is for arguments to functions which are given, but
(possibly because of an early Slate of development) not used. For instance,
(defun program-deterministic-p (program)
(declare (ignore program»
nil)
which defines a function which takes a program as an argument, and returns t if it can be
detennined that is detcnninistic and it is, nit otherwise. The other common use is with special
binding constructs where something must· be specified pOSitionally, but what is obtained from that
position is not needed. For instance,
(defun mod (x y)
(multiple-value-bind (quo rem) (floor x y)
(declare (ignore quo})
rem) )
which is how mod could" be defined; see page 81-mod is defined to be the second value
MC:NILMAN:DCLS 31
23-DEC-83
- "
.. _ ,_ C",
., or ~ , ~ •
• " ~,
~. ~, ",."
-" - .' - .". :. ." -;. .:,' • " • ' - .' > - - , "-" '", "'"' " ~,

_'
.-,,:'
- .' 0 ':'. ~;".
y ''- • _ ,- _". •
NIL Manual 45 Local Declarations
returned by the COMMON USP floor function.
In the current NIL compiler. a variable declared with ignore but actually referenced. will
probably °not be detected. and will produce (erroneous) code just as if the variable had never
been bound
(type type var-I var-2 .•• var-n)
(type var-I var-2 •.. var-n )
These declare that the specified variables are of the type type. For the first fonn. type may be
o
any valid type specifier (see section 4.1.1. page 16). For the second. only certain type specifiers
which are symbols will be recognized: in the current NIL compiler. only fixnum is recognized.
(The symbols flonum and notype are rccognized for MACLISP compatibility.)
The current NIL compiler simply recognizes this declaration and throws it away.
6.1.3 Declarations Affecting ~ompilation Strategies
These de(' lrations make no statements about the program, so (in the absence of compiler
bugs!) can have no effect other than efficiency on programs which are correct.
(optimize (quality-/ value-I) (quality-2 value-2) ••• )
The optimize declaration is used to ten the compiler how it should go about making decisions
when it compiles code, in" a fairly general way; there are four different qualities which may be
specified. Each may take on a value which is an integer from 0 to 3 (inclusive); 0 says that that
aspect should be discounted completely. and 3· says that it is very important. The default value
for each is 1. The qualities are:
speed
Speed is of the essence. The compiler should try harder to make the code run faster.
Obviously. doing so is going to have to trade off against at least one of the other
following qualities-if it did not, then the compiler wouldn't have to make a choice.
space
This quality attempts to quantify for the compiler how important compactness of code is.
safety
This attempts to quantify to the compiler how important the "safety" of the code is. The
exact meaning of this is somewhat hazy; the NIL compiler takes it to mean that operations
should detect erroneous inputs and situations when possible. or barring that, at least do
things so that they might be less likely to trash your environment irrevocably in such a
situation.
compilation-speed
The speed of compilation. In the NIL compiler, specifying a higher value for this quality
will make it do a bit less in the way of minor or special-case optimizations which do not
affect program operation all that much, individually.
What the NIL compiler does for the various values of these qualities is discussed in section 24.2,
page 246.
MC:NILMAN;DCLS 31
, .-. --
-. • • < <
. . ~ ~,' ~~ -' ~ . ~ ~ _ .
• • _ ~ ~'_ .... - ,.. > ~ _ ~.;o _ '. r _
"_

Proci&un.lliUlls: Glob4t1 I >edarations 46
Nil. Manual
( i n 1 i ne jUllc/iowl JUIlC/iOIl-2 ••• )
(notinline jUllction-1 jUllctioll-) ••• )
Theintine declaration says that the compi1er should attempt to code cans to the named functions
'·in Hne"-that is. essentially codc the body of thc function in placc of the call to the function.
The notinline declaration says that this should not be done. Becausc the SIL compiler nonna11y
in line-codes anything it knows how to. the inline declaration is really only useful in NIL to
shadow a notinline declaration.
There arc a couplc· reasons why one might specify that a function not be coded inline. First.
things like trace (page 220) c~m only '·trace" the function calt if there actu,dly is a function call.
S~cond. inlinc compilation. while il does not always eliminate error checking, sumetimes
aggravates dehugging hy causing an error to be signalled other than where it w(}uld ha\'c been in
the interpreted code. ur (worse yet) causes some other error to happen.
The compiJer is free to ignore the inline declaration: if it docs not know how to inline a
function. it simply cannot do so. However. anything declared notinline will be compiled as a
function call. It is an erfor to specify this for a specia1 fonn. e.g.. condo and it is prubably
meaningless and ~I'! addition an error to do so for a macro~
It is important to note that many functions in !\IL provide an intennediate possibility between
complete open-compilation without error checking. and calling the regular function: there is a
large body of special subroutines in the NIL kernel which have caHing sequences optimized for
how the compiler can compile calls to them. but which do error checking. This means that. for
calL cllthough one docs lose trace "lpabiJity. and the visibility of the function can on the stack
when it is examined with the debugger. Whether such routines code as these "minisubr" calls or
are completely coded inline without error checking (where that is possible) is general1y controned
by the optimize declaration. The detailed low· level specifics of this are discussed in section 24.2.
page 246.
6.2 Proclamations: Global Declarations
Often one wants to make . declarations "globally". For instance. to assert that a panicular
variable is· always special, to set an optimization parameter for the compilation of entire file. etc.
The function proclaim is used for this.
procl aim &rcst del-specs
Each del-spec is a declaration specification (just like for decfare-see the beginning of the
previous section). However. it is put into force "globally". Many of the decJarations one
may m.ake with proclaim are similar to those onc might locally declare with declare,
. however their semantics arc different because of their global nature. They are listed
below.
Note: it seems the CO\1MON LISP proclaim only takes one dd-spec argument?
It is imponant to nole that proclaim subsumes previous usage of declare which was not in a
special position (as described in the previous section). While declare in NIL is still accepted in
ttabnonnal" positions (and might continue to be indefinitely for MACUSP compatibility), usc of
MC:NII.MAN:DCLS 31
" . - ~.... ~ , ~~
, ,
, '. :',' '. .~:... -. • , '-. ~', ' : . - .' • , -.' -', " >~.' ,,-"'"' ~ -.. .• ,. ~,; "-'.- ,-~

Nil. Manual 47 Declaring tlle Types of Fonns
proclaim is recommended to emphasize the nature of the declaration.
proclaim evaluates its argument.
Also. remember that
The ~IL compiler will recognize caIls to proclaim at top-level within a file. and. if the
argument to it is constant (Le., it is quoted). put that declaration in force for the remainder of
the compilation, in addition to outputting it to' the file: that it, it is as if it gets wrapped by
(eval-when (eval compile load) ... ) (see eval-when, page 25).
(special l'a~1 var-2 .•. \lar-Il)
A special proclamation not only globally declares that all of the named variables should be
referenccd special. but also that all bindings should be special. Howc\cr. one nonn~ll1y uscs
defvar (pagc 24) without an initialization fonn to globally dcchtfC a variahle special. or. whcn
giving an initialization. uses defvar or defparameter.
(type type vor-l var-2 •.• \'or-Il)
Syntactically. this is the same as the rcgular type dcclaration. Howcvcr. the type information is
associatcd with the special \'all!~s of the variables. not with lcxically bound variah1es of thc same
names. so this is typically p;~'red with a special proclamation. or with defvar (pagc 24),
defparameter (page 24). or defconstant (page 24).
~Il..
of course, ignores this right now.
6.3 Declarin2 the Types of Forms
Often one might want to associate type infonnation with a fonn. wherc there is no variable '
being bound. The the special form allows one to do this.
the type-specifier [onn
the declares that the value returned by the evaluation [oml is of the type type-specifier.
Were the compiler to do nifty things with type constraining. use of this could greatly
enhance its ability to optimize: currently. the compiler generally throws away the type
information. with the exception of a rare misguided special-form which explicitly looks for
a the form. The NIL interpreter. however. does verify that the returned value is of the
specified type.
The type-specifier may be any valid type specifier. and also may be of the fonn
(values ~pespe~l QP~pe~2 ... ~pespe~n)
in which case the returned values must be of the specified types.
MC:NILMAN:DCLS 31
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Sequences 48 NII~ Manual
7. Sequences
A sequence is considered to be either a list or 'a vector (which is by definition a onedimensional
array). NIL supports a number of operations on sequences, which may be applied
equivalently to lists. vectors. strings. and bit-vectors.
Many sequence function take start and end arguments to delimit some subpart of the sequence
being operated on. As a general rule. the slart is inclusil'f.'. and the end is exclusive: thus the
length of the subsequence is thc difference of the elld and the starl. The start typically defaults
to O. and the end to the length of the sequence. Also.' the end. where it is an optional
~.rgurnent. may be explicitly specified as nil. ,md will sti1l def4111lt to' the length of the sequence.
Thus.
( fin d ile111 sequellce)
searches the entire sequence.
(fi nd ilem sequell('(' : start 5)
and
( fin d ilel11 sequence :! ~:-. art 5 : end nil)
search from clement numher 5 onward.
(find ilem sequ('lIc(' :end 5)
checks the first five clements, and
(find ile111 sequence :start 5 :end 10)
searches the subsequence (which has a length of 5) which consists of the clements with indices 5,
6, 7, 8. and 9~
Functions which operate on two sequences generally take the start and' end for each of the
sequences separately: these are kcyworded arguments named :staru and :end1 to specify the
subsequence of the first sequencc. and :start2 and :end2 to specify the subsequence of the second
scqucnce. See, for insL1ncc. replace (page 52).
Many sequence functions (and many other functions) pcrfonn comparisons of various sorts.
For instance. find searches for an item in a sequence. (find item sequence) looks for an· element
of sequence which is eql to item, and returns that element. The particular test used may be
customized: a different test function may be spccified by use of the :test key worded argument, as
in
(find item sequence :test #'equal)
which uses equal rather than eql. The sense of the test can be reversed by using :test-not
instead of :test:
(find item sequence :test-not #'equal)
returns the first clement of sequence which is not· equal to item.
Often. what one wants to compare against is not each element of the sequence. but some
subpart of each clement For this, rather than composing a new :test function. one may specify
a:key function. For instance,
(fi nd ilem sequence : key # tear)
will return the first clement of sequence whose car is eql to item. This may also be used with
:test or :test-not. Note that the key function is only applied to clements extracted from
sequences. ncver to things like the item argument to find.
MC:NII.MAN;SEQUEN 19
2J-DEC-83
~ • '- _' ~ • _ ...... :- .-,o;.~ ~. • ~,-
, ~ "- " ~ ~ - - ~ . -
__ . ,.,>._. , " ".;';,,"";:"".' _"";~;~:.,~:.-,~,, , .... ,.:,_ .. -:.:. ,.-. -~'~ ... ~~~.-~J.>~. '-'':''''::'~' , .... , .. - '.' """.:_.:';,

2
fi .-
Nil. Manual 49 A"e~sing Sequences
Another c1ass of functions do "searching" by means of a unary predicate. These functions
invariably come in pairs: one in which the test is satisfied if the test function returns a non-nil
value. and one in which the test is satisfied if the test function returns nil: for instance.
position-if and position-if-not. and assoc-if and assoc-if-not. Often these functions also take
a :key keyworded argument also: if that is specified. then that function is applied to the datum
being tested and the result given to the test function. For the sequence functions. the datum is
the clement of the sequence being examined.
Final1y. for things which go grovelling through sequences sequentially. one may specify the
direction by usc of the :from-end keyworded argument. which if not nil means that the result
will he as if the subsequence was processed from the higher to tower indices. rather than from
lower to higher. Unless explicitly specified f()f a particular function. it may nul be depended on
that the sequence is actual1~ processed in that order. only tllal the end result is the same: for this
reason. it is generally a bad idea if the comparison or key functions have any side effects. or
depend on the ordering of the clements on which they arc called.
7.1 Accessing Sequences
81 t sequence index
This is the general sequence access function. It returns the indexth clement of sequence:
the index is taken to be 7.ero-origined. This will work generally on lists. vectors. strings
(which are by definition vectors anyway). etc. One may modify an clement of a sequence
hy 11sing setf For inst~T'!("e.
(setq V (make-vector 10»
=> #(nil nil nil nil nil nil nil nil nil nil)
(setf (e1t v 6) 'fool
=> foo
And now,
v => #(ni1 nil nil nil n11foo nil nil nil nil)
It is an error for index to be negative, or not less than the length of sequence as defined
by length. This' means that it is an error to index p~ss the end of a list (in this elt
differs from nth. page 57). and also in its treatment of vectors with fill pointers (the fill
. pointcr defines the length-to access anywhere within such a vector, use aref (page 103».
1 ength sequence
Returns the length 'of sequence. If sequence is a vector with a fill pointer, the fill pointer
is returned. In NI~ length will detect a circular list. and signal an error; in other
imp1ementations. it may fail to tenninate-contrast the definition of list-length, page 59.
If sequence is a list. it is an error for it to not terminatc in nil-in this, length differs
from previous implementations of NIL.
MC:NILMAN;SEQUEN 19

Creating New Sequences 50 Nil. Manual
7.2 Creating New Sequences
Many functions which create sequences take an argument which is the type of sequence to be
created: it is typically caHed the result-type, or perhaps just the type. This may be, in general. a
type specifier suitable for use with typep, but must of course be a subtype of sequence-that is,
a SUbtype of list or vector. The type of sequence created will be the most specific type of
sequence which is a subtype of that specified type. At this time. the ~IL sequence code has not
been integrated with the 1'11. array type code. so it is possible that complicated type specifications
will not work. The filllowing typcs wi11 always work: list. string. simple-string. bit-vector.
simple-bit-vector. simple-vector, and vector. vector. which is rcaH), an ahbreviation for the
type specifier (array • (.». i.e.. a one-dinlcnsiomlt array of unspecifiedc1emem-type. will create a
vector of clement-type 1. i.e.. a general '"ector.
mal f •••••• "
Creates a sequence of type reSull-/.lpe (as might be given to make-sequence). and stores
in it the concatenation of aU the clements of sequences. For instance.
(concatenate 'string "foo" "bar" ~baz")
=> "foobarbaz"
(concatenate 'list "foo" "bar" '(1 2»
=> ('\f '\0 '\0 '\b '\a #\r 1 2)
subseq sequence start &optional end
Returns a sequence of the same general type as sequence, containing clements from start
up to (but not including) end.
(Subseq "faa on you" 4) => "on you"
(subseq "faa on you" 4 6) => "on"
(subseq "faa on you" .4 3) => is an error
(subseq tea b c d) 1 3) => (b c)
Note that the result of subseq never shares with the original sequence. Thus. (subseQ
lisl 5) is not the same as (nthcdr 5 list). In fact. subseq would signal an error in this
case if the list did not have at least 5 elements.
The result of subseq wi11 always be a simple sequence; if, for instance, sequence is an
adjustable array of element-type string -char and has a fill pointer. the result will just be
a simple string.
MC:NII.MAN:SEQUEN 19
23"DEC-83
~ ~ ~ ~, r-\~ ~
, "
.. , ~ - " ~
~ \- ¥ ....,
• :~,"
"
"" • : ' " ';',," --:~
.-:
,,' " ' .. ~",:..:.:;'. ". '., - - , ' " : - , - '", • - - , •• '~ -
- >

NIL Manual 51 Searching through Sequcnccs
copy-seq sequence
Copics thc sequcnce sequence. This might be neccssaryif the rcsult is going to he
modified. for instance. 'Inc result of copy-seq will always be a simple sequence. as
described undcr subseq.
See also thc map function, page 54. which produces a sequence of the results of applying a
function to the corresponding clements of some input sequences.
7.3 Searching through Sequences
fin d i/{'m SClI1U'I1U' &kcy from-end slar! elld leSI lesl-not kcy
find searches through the specified subsequence of sequencc until it finds an clement which
satisfies the specified comparison ,lgainst item. in which case it returns thal clement: if no
,match is found. find returns nil. If a non-null from-end argument is specified, then the
result (if there is a match) will be the "rightmost" clement which matches ilem, otherwise
it will be the "leftmost".
fi nd-1f Icsl sequcl1ce &key from-end Slarf cnd key
fin d - 1 f - not lesl scquence &key from-end sian elld key
find - if returns an clement of the specifed subsequence of sequence which satisfies the
function ICSI. or nil if no such clement is found. If a key argument is specified, then lesl
is called on the result of calling key on an clement of the sequence: otherwise. lesl is
called on the element directly. If a non-null from-Pl1d argument i~ ~pccifiec1, thpn rhp
result will be the rightmost such clement within the subsequence: otherwise. it will be the
leftmost.
find -if-not is similar. but succeeds if the result of calling test is nil.
pos 1 t 1 on item sequence &key from-end start end test test-not key
If there is an clement of the specified subsequence of sequence which matches item
according to the specified test, then position returns its index (the index within sequence.
not within the subsequence); otherwise. position returns nil. If a non-null from-end
argument is specified. then the result is the index of the lefunost element satisfying the
test; otherwise. it is the index of the righunost such element.
pos it ion-if test sequence &key from-end start end key
position-if-not test sequence &key from-end start end key
pOSition-if returns the index of an element within the specified subsequence which
satisfies the test function lest. If key is specified, it is a function called on the element of
the sequence. and that result is given to test instead of the clement itself. If a non-null
from-end argument is specified. then the index will be of the rightmost such clement:
otherwise. of the leftmost. If no such clement is found in the subsequence, nil is
returned. As with position and all similar functions, the index is the index within
sequence. not within the subsequence.
position-if-not is similar, but succeeds if the result of calling test is nil.
MC:NII.MAN:SEQUEN 19
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. Qig~ .. h4iWJJllU. • .i a LJ 71
Misccllmlcous Opcratiuns on Sequences 52 Nil. M411lual
count ilem sequence &key from-end Slarl elld I('SI tl'SI-Il(J/ key
count rcturns the count of clements within the specified subsequence of sequence which
satisfy the specified comparison against item. The test function may depend on the order
in which the clcments arc processed: if a non-null from-end argument is specified .. then
the clements will be processed from right, to left (Le.•
decreasing· indices); otherwise. from
left to right (increasing indices). As usual, the first argument to the test is item. and the
second is the clement of sequence if no key is specified, otherwise the result of calling key
on the elemenl
count-1 f Irsl srqucl1ce &key from-cnd Slar! end key
count-if-not Irsl srqurll('(' &key Ji-om-clld slart elld key
count-if rcturns the count of tile element~ of suhscquence which S4uisfy thc unilry
predicate lesl. If no kcy is specificd. lest is caned on tile cIement~ of the subsequence;
otherwisc. it is called on the result of applying key to ench clement If a non-null fromclid
argument is specified. tilen tile c1ement'i are processed from right to left (decreasing
indices), otherwise from left to right.
count-if-not is similar. but reverses the sense of lesl.
7.4 l\liscellaneous Operations on Sequences
reverse sequence
Returns a copy of sequence. with the clement, in the op!,ositc order_
nreverse sequence
Reverses sequence, destructively; it does not create a copy. Note that if sequence is a list.
one should always use the return value of nreverse: that is. do something like
(setq 1 (nreverse 1»
rather than just
(nreverse 1)
This is in genera] true for all destructive list operations. such as sort and delQ. The
reason is that although the cons cells of the input list are reused. the pointer returned is
not necessarily the same as the originalftfirst tt cons of the lisL
fill sequence element &key start end
Replaces the elements of sequence with element, from start (default 0) up to end (default
length of the sequence).
(setq a '(0 1 2 3 4 5 6»
(fill a nil :start 2 :end 4)
=> (0 1 nil nil 4 5 6)
And now,
a => (0 1 nil nil 4 5 6)
rep 1 ace sequence! scquencel &key starl! end! s1art2 endl
Replaces the clements of the specified subsequence of sequence} by the elements of. the
specified subsequence ofsequelice2.
MC:NII.MAN:SEQUEN 19
23-DEC-83
. ~ , ' -
.' > ":: " ' , :'.:: :., . ..: ,~>.::,.;' .",: :,""c..'" ,'" "" "

Iteration over Sequences 54
NIL Manual
substitute-1f nrw lrsl spquellce &key from-end Slart end key ('ou",
substitute-if-not new lest sequence &key j;om-end slart end key COUIlI
Similar. by extension.
nsubst1tute new old sequence &1cey /rom-elld slart end test les/-not key count
The destructive version of substitute; sequence is modified.
nsubstitute-1f new lest scquence &key /rom-e1ld start end key counl
nsubs t 1 tute-1f-not new test sequellce &kcy /rom-el.ld start end key count
Similar.
7.5 Iteration over Sequences
The fi)lIowi,ng functions iterate a user-specified function over one or more sequences in various
ways.
map rcsu/t-typc junctioll &rest sequellt~es
'111is is the general sequence mapping function. Nute that this is different from the
MAC'l.ISP and LISP MACHINE LISP map function. which is renamed to mapl by COMMON
USP.
The result is a new sequence of type result-type (see section 7.2. page 50). containing the
results of applying jUliction to the clements of sequences. There must be at least one
srqllenee specified: junction gets as many arguments as there are sequences-first it gets
called on all of the first (index 0) clements. then on ,,11 the second clements. etc. The
iteration tenninates when the end of any of the sequences is reached. so the result will
have the same length as the shortest input sequence.
(map 'list #'cons "abc" '(a bed e f»
=> (#\a . a) (#\b • b) (#\c • c»
If result-type is list. and the input sequences are all lists. then this is effectively the same
as mapcar (page 31).
some predicate &rest sequences
some applies the function predicate to the corresponding elements of sequences (of which
there must be at least one), in order. If the result of some application is not nil, then
some immediately tenninates the iteration and returns that value; if all the applications
returned nil. some returns nil.
The predicate may depend on being called on the elements of the sequences in order.
Only as many elements as there are in the shortest sequence are processed.
The effect of this may also be obtained by use of the thereis clause in the loop macro
(page 144).
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NIL Manual 53 Miscellaneous Operations on Sequences
(setq v (make-sequence 'vector 10»
=> #(nil nil nil nil nil nil nil nil nil nil)
(replace v '(1 2 3 4 5 6»
=> #(1 2 3 4 5 6 nil nil nil nil)
v => #(1 2 3 4 5 6 nil nil nil nil)
The number of elements transfercd is the minimum of the lengths of the two
subsequences, i.e.,
(min (- end! startl) (- end2 start2»
remove ilrl11 srquence &key /rom-end slart elld leSI tesl-lIol key COUllt
remove returns a copy of srquem'c of Ule S.lI11C general type. except that clements within
Ule specified suhsequence which match ilem according to the specified test arc not copied.
If Ule COUllt argument is -specified. then it should he a non-negative integer which limit'!
the numher of matching element~ which get "ignored": jf it is not specified. all matching
-clements within the specified subsequence wHl be missing from ule result. The from-end
flag is only really meaningful if a COUIlI is specified: if a non-null from-end is specified.
then the rightmost COUIII c1ement~ of the specified subsl~quence will be missing from the
resul~ otherwise the leftmost.
remove-if tesl sequence &key /rom-end slarl elld key count
remove-if-not tesl sequence &key /rom-end slarl end key COUllt
Like all similar extensions.
de 1 ete f!rn: ~rqur::('[' &kcy from-end start end test lest iwi key COUiii
'J11is is the destructive version of remove. q. v.: it will attempt to use sequellce to
construct its resu It The result mayor may not be eq to sequence. and sequence mayor
may not be actually modified to produce the result: NIL will attempt to do this the "best
way" it can. For this reason. delete should ullly be used for value, never strictly for
effect.
delete will succeed in side-effecting sequence to produce its result jf sequence is (1) a list,
(2) an adjustable vector of any type, or (3) a vector with a fin pointer. The result is still
not guaranteed to be eq . to sequence.
de 18 t 8 -1 f lesl sequence &k ey from-end slart end key count
delete-if-not les/ sequence &kcy /rom-end start end key count
Similar, by extension.
subst 1 tute new old sequence &key from-end slart end lesl test-not key count
substitute returns a new sequence in which the elements within the specified subsequence
matching old according to the specified test have new substituted. While substitute does
not modify sequence, the result may share with sequellce; in particular, if sequence is a
list, the result may share a tail.
If a count argumcnt is specified. then this is a non-negative integer which limits the
number of substitutions madc. In this case. specifying a non-null from-end argument
causes the rightmost COUIlI clements matching old to undergo substitulion. otherwise the
leftmost.
MC:NILMAN;SEQUEN 19
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NIL Manua} 55 Sorting Sequences
every predicate &rest sequences
l.ike some. but returns t if thc result of applying predicate to the clements of sequences is
ncvcr nil: if some app1ication of predicate is nil. then every terminatcs immediately and
rcturns nil.
The effect of this may also be obtained by use of the always clause in the loop macro
(page 144).
not any pr('dicate & rest sequences
Returns t if the rcsult of applying the function predicate to the corrcsponding clements of
scqU(,IIC(,S is alw,lYs nil: if the result of that application is not nil. then notany
immediately tenninates thc itcration and returns nil.
The cffect of this may also be obtaincd by usc of the never clause in the loop macro
(pagc 144).
notevery predicate &rcst sequences
If the result of some application of predicate to the corresponding clements of sequences is
nil. then notevery tenllinates its iteration and returns t: otherwise. it returns nil.
7.6 Sorting Sequences
sort sequence predicate &k~y key
This is the (,OMM01' LISP sort function: when it is used without a key. it is MACI.lSP
compatible.
sequence is destructively sorted according to thc predicate predicate. which receives two
arguments and should return a non-null value only if its first argument is strictly less than
its second argument. If key is spccified. then it is a function of one clement which is
applied to the sequence element before being passed on to the predicate.
For MACLISP compatibility, if sequence is a list. then the sort is stable; equiva1ent pairs of
items (those where the two keys are neither strictly less than each other) remain in their
original order. When sequence is a vector, a quicksort algorithm is used.
sortcar sequence predicate
This is provided for MACLISP compatibility. It is just like
( so r t sequence predicate : key II' c'a r )
stab le-sort sequence predicate &kcy key
Like sort. but guarantees that the sort will be stable (sec sort). If sequence is a vector,
thcn a bubble sort is used.
MC:NII.MAN:SEQUEN 19
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Lists
8. Lists
Note also consp (page 18). listp (page 18).
S6
Nil. Manual
8.1 Creating, Accessing, andl\1odifying List Structure
car COilS
cdr cons
c ...• r cons
'II dcfincsaJt compositions of car ,md cdr up to four levels deep; Illr insk1nce. (cddar
COilS) is equivalent to (cdr (cdr (car elms»).
Actually. COilS may be either a cons or nil: the car and cdr of nil arc alwa)'s nil.
Nonnally in NIL car. cdr. and their compositions compile into special subroutine cans
into the !'Il. kernel which do error check~ng. but arc much faster than function ca11ing.
Directing the compiler to produce faster code by usc of the Sf eed quality in the optimize
declaration will cause all of these accesses to be completely inHne coded, witht}lu
checking: sec section 24.2. page 246. (In NIL. car and cdr each Like only one
instruction. )
AlI of these functions may be used with setf in order to update the panicular component
of cons.
rp laca ('OilS new-car
rplacd cons new-cdr
rplaca modifies the car of COilS to be flew-car, and returns cons: rplaca modifies the
cdr. Sec also setf (section 5.9, page 38) which can be used to update any of the above
car I cdr references.
These functions, and the use of setf with car, cdr. and mends. are normally coded by
the NIL compiler as special subroutine caUs into the NIL kernel which do argument
checking. but are faster than function calls. Use of the speed quality with the optimize
declaration may override this; see section 24.2, page 246.
f1 rst list
second lisl'
th 1 rd lisl
fourth lisl
fifth lisl
sixth Iisl
seventh lisl
eighth lisl
ninth lisl
tenth lisl
car, cadr, ctc. lbese may all be used with setf.
MC:NII.MAN:LIST 37
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NIL Manual 57 Creating. Accessing, and Modifying Lisl. ..
Note that the names of these functions use one-origin indexing:
(third x) (nth 2 x)
rest list
cdr. This may be used with setf.
nth index list
Returns the illdextl1 clement of list. zero origined. Note also tl1at this takes its arguments
in a different order than 'elt (and other more specialized sequence accessors).
If illt/ex is not less than 111e length of lisl. nth returns nil by analogy to car and cdr. In
111is it also differs from elt.
nthcdr mimes list
, Relurl1S list after mimes cdrs have been taken on it.
Note also tl1e t reader-macro (section 20.1.1. page 216). which is convenient for creating list
structure in template form. especially if large portions of it are constant. and push (page 38) and
pop (page 38) which can be lIsed lO maintain a list in FIFO fonn in an arbitrary setfable place.
cons x y
Makes a cons whose car is x. and whose cdr is y.
ncons x
Equivalent to (cons x nil).
xcons x y
"Exchanged" cons. Equivalent to (cons y x). This function is not nonnally used~ it is
inherited from MACLISP. where its existence is mainly for me benefit of me compiler in
rewriting calls to list into calls it could chain together the computations of better:
(list x y z)
==> (xcons (xeons (ncons z) y) x)
11 s t &rcst elements
Returns a freshly created list of its arguments.
(list) => nil
(list 'x) => (x)
(list 'x 'y) => (x y)
11 st. first-thing &rest other-things
Sort of like list. but the last argument to list. is used as the cdr of the final cons.
instead of nil. Alternatively. it may be thought of as many nested conses:
(list- 'a) => a
(list. 'a 'b) => (a. b)
(list. 'a 'b 'e) => (a b . e)
(list- fa 'b nil) => (a b)
MC:NILMAN:LIST 37
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Creating, Accessing. and Modifying List .• 58 Nil. Manual
make-l1 st size-of list &key il1i1ial-elemelll
Creates a list of nils size-offisl lung. whose clemcnl~
nil).
arc inilial-elemeflf (which defaults to
append &rcst lisls
(append x y) returns a list which has first all of the elements of x, fol1owed by all of
the clements of y; for instance.
(append '(a b) '(x y» => (a b x y)
The subpart of this list (in the example. the cddr) is the original last argument to
append: append never copies its last argument.
(append x )' z)
==> (append x (append y z»
When given une argument, append returns that argument: with no arguments, it returns
nil.
If just copying a list is desired, it is stylistically better to usc (copy-list /is/) (page 59)
rather than (append list nit).
revappend list I Iisl!
This is like (append (reverse lisll) !ist!). but is more effident because it only has to
make one pass over listl.
last Iisl
RNllrn, rhl' l~~t (,one; of lis, (!!!H th~ last e!('m~nt!). un!~ss lis! i~ nil. in ',I,'hkh c~ze it
returns nil. In r\1L. last deals properly with a non-nun last cdr of /isl. The only noncons
it will accept as an argument howcyer is nil.
(last '(1 2 3 4 5» => (5)
(last '(a b . e)} => (b. c)
(last nil) => nil
nco n c &rest lists
Joins together all of the lists by destructively modifying them. Specifically, for each of
the lists which is not nil~ the final cons (as might be returned· by last) is modified by
rpJacd to be the next list
(setq 11 '(a b»
(setq 12 '(x .v»
(ncone 11 12) => (a b x y)
and now,
11 => (a b x y)
One should be careful. however, about using ncone strictly for. effect (i.e., not using the
returned value), because if the first list is nil (the empty list) the desired side-effect will
not occur.
nreconc listl list2
'Ibis is like (ncone (nreverse Jisll) lisI2), but can be faster because it only has to make
one pass over lisil.
~1C:NII.MAN:LIST 37
23-DEC-83

NIL Manual 59 Creating. Accessing. and Modifying List ...
list-length list
list-length returns the length of the list lisl. If list is circular. then list-length returns
nil--in this it differs from length, which in r\lL will signal an error but in other COMMON
LISP implementations may fail to terminate.
It is an error for Iisl to not tenninate with nil (assuming it is not circular). In this, listlength
differs from its implementation in previous releases of NIL.
copy-l1 s t list
Copies the top-level cnnses of list. This may be used to replace the common idiom
(append lis/ (»
and. additionally. handles a non-null last cdr of lis/ gracefully.
copy-alist a-lisl
Like copy-list. and additionally. each top-level clement of a-list which is a cons has that
first cons copied also (1101 tJle entire top-level of the a-list cntry).
Note that this function name contains "alist", a term which is spelled "a-list" everywhere
else now.
This replaces the LISP MACHINE LISP function copyalist, which exists identically in NIL.
copy-tree tree
Returns a copy of tree. Recurses through both the car and the cdr. tcrminating at nonconses.
That is. only conses are copied. This replaces the old MAC'l.lSP idiom
(subst nil nil "eel
which has been changed incompatibly by COMMON LISP (page 60).
This function is thc COMMON I.ISP equivalent of the LISP
function, which is defined in NIL as a synonym for copy-tree.
MACHINE LISP copytree
butlast list &optional (n/)
This returns a copy of lisl, but without the last n elements. If the length of the list is
less than or equal to n, nil is returned.
(butlast '(1 2 3» => (1 2)
(butlast '(1 2 3) 2) => (1)
(butlast '(I» => nil
(but1ast nil) => nil
nbut 1 ast list &optional (n I)
Destructive version of butlast: the last n elements of list are "spliced out", by rplacd.
nbutlast should be used for value. however, because if the length of the list is less than
or equal to n, nil is returned and no "splicing" is perfonned.
ta 11 P sublist list
tailp returns t if sublist is a sublist of list. nil otherwise. What this means is that after
taking some numbcr of cdrs of list (possibly l.cro), one gcts to a list eq to list.
MC:NILMAN:LIST 37

Substitution 60 NIL Manual
1 d 1 ft list sublist
If (taiJp sublisl list) is tnJe,ldiffC"1ist differencc") returns a list of the clements of lisl up
to but not including sublist. This is the same as .
( nbut 1 as t list (1 ength sublist})
If (tailp sublist list) is false. Idiff simply returns a copy of list.
8.2 Substitution
These functions arc extensions of the subst and subJis functions which are defined by
\1:\('1 ISP and liSP MAClIl~F IJSP. NOle LI),ll LIley by dcfhult usc eql to lest for equality; Lllis is
incompatible with MACI.1SJl mld an e,lrly release of Nil.. in which subst used equal but sublis
lIsed eq (but only worked on symbuls). A different tcst may be specified by usc of the :test
keywordcd arg~lment: this is a predicate of two arguments used to test "cQuality". )f it is more
convenient, the sense of the predicate may be reversed by usc of the :test-not keyword.
Note also thatthcse functions only descend through list structure ('·trees")~
inside of vcctors. arrays. or other structures.
they do not 100k
subst new old tree &key test lest-not" key
R cturnsa copy of tree. with n('w. substituted when a of the tree matches old according to
the test.
This is incompatible with MACUSP subst. in that the result is 1101 guaranteed to always
copy even if substitution is not perfonned. TheMACUsp idiom (subst nil nil lrer) is
replaced by the copy-tree function (page 59). Be on the lookout for the use of this
idiom in old code. for it can cause obscure bugs when uncopied structure is modified.
The Nil. compiler will warn about usc of this idiom and turn the subst into a ~1n to
copy-tree if (1) there are no keyworded arguments supplied (2) Ilewand old arc constants
determinable at compile-time and (3) their values are eql. The runtime function cannot
detect this idiom.
nsubst new old tree &key lest lesl-.nol key
Like subst •. but does not copy: the new components are destructively stored in tree.
However, this should be used for valuc, for if tree matches old.- the result is new but no
bashing of list structure is done.
sub 11 s ~list tree &kcy lest lest-llot key
Like subst. but performs substitution for several things. at once. a-lisl is an association
list of the· objects to match. and their replacements. For example,
(sublis '«yes. no) (t . nil» '(t generally means yes»
=>(n11 generally means no)
sublis. remember, looks at cars and cdrs equivalently. If we attempt to invert the above
example. we get
(sublis '(no. yes) (nil. t» '(nil generally means no»
=> (t generally means yes . t)
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NIL Manual 61 Using I ,ists as Sets
nsub 11 s a-list tree &key test test-not key
I.ike sublis. but destructive. See also nsubst.
8.3 Using Lists as Sets
One common use of lists is as sets of objects~
of functions for doing this.
NIL (and COMMON LISP) provide a complement
All of the functions take similar arguments. NonnalIy. they use eql as their predicate. so that
they work on numbers properly also. If this is not suitable for the purpose. then a predicate may
be specified by gh'ing it as the :test kcyworded argument. For instance.
(union '«a b) (b) (e» '«d) (e) (a b) (b» :test "equal)
=> «a b) (b) (e) (d) (e})
The scns~ of the predicate can be reversed by using :test-not instead of :test.
Sometimes the c1ements of the set arc d~lt41S1ructures of some sort. and one desires to only
compare one part of the datastructure. but not write a predicate to compare things. If thc :key
kcyworded argument is used. then that is a function which will be applied to each clement as it
is tested. and the results of that will be given to the equality predicate, rather than the elements
themselves. for example,
(union '«a) (b) (e» '«d) (e) (a) (b)) :key 'tcar}
=> «a) (b) (c) (d) (e»
The :key-specified function is only applied to elemenL~ extracted from lists, never to sin81~ ilpm
arguments givcn to any of these functions (such as member. below). The ordering of the result
may not be depended on; neither may the result if either of the inputs contains duplicate
clements (as defined by the predicate). nor the particular choice of clement (that is. the one from
the first list or the one from the second I~st). Thus.
(union '«a) (b x) (c}) '«d) (e) (e) (b y» :key "car)
might return either of the sets
«a) (b x) (c) Cd) (e»
or
«a) (b y) (c) (d) (e»
since they are equivalent according to the test criteria.
member item list &key test test-not key
If item is a member of list according to the specified test (which defaults to # 'eql). then
member returns the sublist whose car satisfied the test. Otherwise. nil is returned. The
other functions in this section (Ire implemented in terms of this. Note that if a function is
specified with :key, it is only applied to items of list. not to item.
Note that the default predicate for member. # 'eqJ. is incompatible with MACLISP member.
This provides consistency with an other similar functions.
memq item list
This is member with a test of # 'eq. memq is not defined by COMMOl' USP, but is
inherited from MACIJSP. It is specially handled by the NIL compHer.
MC:NILMAN:I.IST 37
23-DEC-83

• _ .,
Using Lists (is Sets
un ion lisll lis/2 &key
set-difference Ii.'ill lisl} ,&kcy lesl leSI-no/ key
} are used to constructthc result.
Rcturns the set diffcrence of lisl! and lisl} (a list of the elcments of lisil which arc not
present in lisl2. according to the predicate).
nset-difference list! lisI2 &'key leSI leSI-I1o/ key
IJcstructi\,c set-difference: the result is constructed from the conses of lisil and/or lisl!.
set-exclus ive-or lisll lis12 &key leSI lest-nol key
Returns a list of the clements which occur in eithcr lis" or lis/}. bill not both. according
to the predicate.
nset-exclusive-or listl list2 &key leSI /esl-1101
Destructive set-exclusive-or: the result is constructed from the conses of lisil and/or.
list2.
subsetp Iisll lisl2 &key lesl IttSI-110/ key
Returns t if lisil is a SUbset of (bUt not necessarily a proper subset of) lisa. nil otherwise.
adjoi n item lis/ &key leSI lesl-not key
If ilem is a member of lisl according to the specified test, this just returns lisl: otherwise.
it conscs ilem onto the front of list. and returns thal adjoin could have been defined as
(defun adjoin (item list &rest keyworded-args
&key test test-not key)
(if (apply #'member item list keyworded-args)
list
(cons item list»)
which also shows the utility of the &rest keyword combined with &key.
key
MC:NILMAN:I.IST 37
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-. . .
. ..' . .:,..::,"'

NIL Manual 63 Association I -ists
8.4 Association Lists
Association lists arc an abstraction built from lists which arc useful in many cases. An
association lisl (or a-list, sometimes misspelled alisl in this document), is a list.. all clements of
which are conses: the car of each cons is the key, and the cdr of each cons is the data
associated with that key. Association list~ differ slightly from just lists used as sequences utilizing
a key of car (or cdr): if an entry in an association list is the atom nil, then it will be ignored
totally. Functions which deal with more general sequences or lists. such as member, find, and
position. would blindly apply the supplied key (e.g.. car) to nil. and try matching this against
the item being searched for.
There are two common ways in which aSSOCiation lists are used. For one. what is being
constructed is basically just a lilb1e with entries of a single key. In this. the entries in the a-list
are cnnses of the key and the data associated with the key. and one uses assoc with an
appropriate test to do the lookup: the data of the key may be replaced by using rplacd on the
result of the assoc. assuming assoc did not return nil. There are two potential disadvantages
with this approach. First, the lookup is linear. so the lookup time grows linearly with the length
of the tahle. How much this matters depends on the efficiency of the equality predicate in usc:
eq is extremely fast. and eql is fairly fast, so this could matter a fair amount if they arc the
predicates in usc. Second. because a-lists arc constnlcted out of C(lnses. they can be scattered all
over \'inual memory and cause poor paging performance: it is possihle for each cons in an a-list
to lie on a different page. If entries are only rarely added to or removed from the table (entire
entries. not just update of the car or cdr of an a-list entry), it might be reasonable to ensure
ta'iut th\: a liSi lk5 ira fairly cuntiguous virtud] Hi(;Jii\ii) b,)' \.:oJ.'yiug it wilil l;(JIJY-i2ii~i (page 59)
when something is added to it. Some rough guesses. with a test of eq: if the a-list has over 50.
entries, it is probably better to use a hash table. For 70 or 80. a hash table is vinual1y
guaranteed to be better, unless most of the lookups wi1l succeed, and find entries near to the
front. For between 5 and 10 entries. an a-list is almost undoubtedly best. and can he optimized
by copying with copy-alist. For values between 10 and 50. the decision on which to use
requires balancing additions and deletions against wasting time (and creating garbage) using copyalist.
Probably it is best to only do the copying with copy-alist for tables which are not updated
in th,e "normal course of program running", i.e., which might only be updated when new files are
loaded.
The other common use of a-lists is where the implicit ordering of a list comes into play. One
entry in the association list might have the same key' as another which occurs "later" in the a-list;
since association lists are always searched in left-to-right order, the first occurence will shadow any
other occurences. A simple LISP lexical interpreter might use an association list to hold the lexical
variable bindings, for instance. "Binding" pushes the new variable/value pair on the front of the
"environment" a-list. and "unbinding" pops the entry off. For this son of use, hash tables do
not present an alternative without some hairy hacking of "contexts".
A third possible use of an a-list is for two-way associations; that is, the car and cdr may
both be viewed as keys used to look. up the other: one uses assoc to find the entry by the car
key, and rassoc to find the entry by the cdr key. Hash tables do not provide this son of
service: if a-list lookup time is prohibitive in a particular case. the alternative is to usc two hash
tables.
MC:NJI.MAN;I.IST 37
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Association l.ists 64 NIL Manual
as soc item a-lisl &key lesl lesl-nol
Searches a-lisl for an entry whose car matches ilem according to the specified test. I f one
is found. that cons is returned; otherwise nil is returned. If a non-null result is returned,
the datum of it may be modified by use of rplacd.
Note also that since the default test is # 'eql, this is incompatible with MACLISP assoc.
To retain the same effect. one must· use
(assoc item a-list :test "equal)
or simply assq (below). Of course. often the choice of assoc in MACTISP is because item
is a number, so equal is not needed in Nil becausc eql compares numhcrs correctly.
ras soc il(,l11 a-/isl &key lesl lesl-l1ot key
l.ike assoc, except that item is matched against each datum in a-lisl. rather than each
key.
assq item a-lisl
This is inherited from MACl.lSP and also .is defined by I.1SP MAClllt\F 1 JSP: it is 1101
defined by CO\1~ON I.ISP. It is identical to
(assoc ilC111 a-Jisl : test #'eq)
Compilation of assqdocs ·1101 produce any different code than the above fonn. so the
choice between the two is between COMMON LISP compatibility and verbosity in the source
code.
r"~~q
i'I'''' n-If~!
'111is is inherited from LISP MACHINE LISP; it is not defined by COMMOT' LISP.
same as
(rassoc item a-list :test I'eq)
Sec assq (above) for more qualifications.
It is the
aeons key datum a-liSI
This is the same as
{cons (cons key datum) a-lis/)
but shows the intent better.
pa 1 rl1 s keys data &optional a-Iist
Returns an a-list made by associating keys and dala and adding them to the front of a-iisl
(which defaults to nil). keys and data must be lists of the same length.
(pairlis '(foo bar) '("Foo" "Bar") '«baz . "Baz"»)
=> ( (foo . "Foo") (bar . "Bar") (baz . "8az"»
The result will share structure with a-list (that is. (tailp a-list paiTIi~result) is 0, so
modifications to the associations in the returned result will atfectthose assocations in a-list
also.
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NIL Manual 65 Symbols
9. Synlbols
9.1 The Property List
See also section 5.10, page 39, which deals with property lists in a more general way.
symbo 1 - P 11 s t symbol
Returns the property list of symbol. Unlike the MACLISP pUst function. this only works
on symbols. not disembodied property lists.
symbol- pHst J11~ly he used with setf to change the property list of a symhoL This is
generally not rec()mmcnd~dpraclicc. however. because doing so might callsc properties
essential to tllC ~Jl. system to be lost.
get sJ'Il1bul indicator
Standard MAC'I.ISI) ·get. The value stored under indica/or on the property list of symbol is
returned: if tllere is no such value. nil is returned. As in MACUSP. symbol may also be a
disemhodied property list. Unlike in MAC'I.lSP. get docs not arhirrarily check the type and
then return nil if it is ncitller a symbol nor a list; in :-';11. one gets an error for an invalid
type.
For both MACLISP compatibility and convenience. get is not going to disappear in tlle
future.
putprop s),mbol value indicator
Standard MACLISP putprop. If symbol already has an indica/or property. tllis replaces it
with value. otherwise puts a new one. As in MACLlSP, symbol may also be a disembodied
property list
COMMO~ LISP does not define putprop: rather. one uses setf with getf (page 39).
putprop is not going to be flushed from NIL, however. Note also that putprop takes its
arguments in a different order from the "standard setf order" in which the value being
s.tored comes last
remprop symbol indicator
Standard MACUSP remprop. If symbol has an indica/or propcrty, then that is removed by
being spliced out of the property Jist. and tlle subHst of tllc property list whose car is the
value (being removed) is returned. If there is no such property, nil is returned. For
instance, if one does
(putprop 'kitty 'yu~shiang 'flavor)
then
(remprop 'kitty 'flavor)
= > ( y u - s h ian 9 and maybe some subllsl 0/ the property list)
. See also the remf macro, page 40 .. for removing properties from property lists stored in
arbitrary places.
MC:NILMAN;SYMBOL 30
23-DEC-83
'.
'
; ~ ---- . ~ ~
. - ~ ~ - .
, ". ,', ~~< .'. . ~ '. "-,'.::,'" .. " ,- - . ~, . ' "'". ..." ..".. '. .. "",', .; "

The Prill( Name
66
NIL Manual
Note: COMMON USP docs not define the actual value returned by remprop. only that it
will be null if the property was not found, non-null if it was. The value returned by NIL
remprop is compatible with MACLISP. and wilJ be retained fi)r that compatibility.
9.2 The Print Name
symbol-name symbol
Returns the name of symbol. which is a string.
Note that a string which is a symbol name should never be modified: ncitJler should the
name of a symbol be changed.
In ~II .•
the name Of.'l symbol will always be a simple string.
The mime of a symhol has variously been calJed a prilll 1Iame and a pname. tenns which
are being phased out but· stiU pervade the NIL implementation.
samepnamep s)'1171
sym2
Returns t if syml and sym2 have equal print names. Case is significant. syml and s)'1112
may be strings too. Either (or both) of the symbols may be specified as strings instead~
samepnamep is reany just a MACLISP function. It is obsoleted by string = (page 113).
because the string comparison functions in SIL will accept symbols and perfonn the
comparison on their namcs.
9.3 Creating Symbols
make-symbol pname
Makes a new uninterned symbol whose print-name is the string pname. It will have no
value or function bindings. no package, and an empty propeny list
That the print-name (as returned by symbol-print-name) of the returned symbol will be
eq to p"ame should not be depended upon.
copy-symbol sym &optional coprprops
If copy-props is nil. then this is the same as (make-symbol (symbol-name S)'111»; that is
t
it returns a virgin symbol with the same print-name as sym. If Coprprops is not nil then
t
the value and function definition and propeny-Jist and package of sym wiJI be copied to
the new symbol.
Actually. the current dynamic bindings (value and function) of sym are copied to the new
global dynamic bindings of the new symbol.
,
copy-symbol with a nun copy-props argument is a reasonable way to generate a unique
symhol which is somewhat mnemonic although not completcJy visually unique. The NIL
compiler copics symbols like if-false to generate tags. for instance: no new print name is
created. just the basic symbol structure. on which· properties can be placed. If the symbol
is to be used as a variable in macro expansions, however. it may be better to use
MC: N I LM 1\ N :SYM BOL 30
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. . - . -
, -' . .. . . . - - .' - '
> .>.>, .. ". >' ••.. " .. "J'~>: .; .• 'i}/:'~ "1:'...,',,) >":, ~";>"

NIL Manual 67 Creating Symhols
gentemp (below).
gensym &optional x
Standard inherited-from-MACLISP gensym. gensym creates new uninterned symbols. The
print name of the symbol is constructed by prepending a single character prefix' to the
decimal representation of a counter which gets incremented every time gensym is called.
The name has been around for so long that automatical1y generated names arc commonly
refered to as geIlSYI1lS, and the act of doing so as gl'flsyming.
(gensym) returns such a constructed symbol.
(gensym lIalll£» sets the prefix to he nalll£>. which must be a string or a svmhol. and
then makes a gensym. (In ~1AC1.lSP. only the first character of name is used: in NIl.. the
entire name is.)
(gensym illteger) sets the counter to i11leger, and then makes a gensym. illIeger must
not be negative.
gentemp &optional prefix package
gensym creates a symbol in a manner similar to gensym. but interns it in package
(which defaults to the current package). Additionally, gentemp guarantees that the
symbol is unique by continuing to increment its internal counter until it succeeds in
constructing a symbol which has nol already been interned in package.
Unlike gensym. the prefix argument to gentemp is not "sticky": that is. it does not
default to the last one supplied. If it is not supplied, it defaults to t. Also, there is no
provision for resetting the internal counter.
Use this for creating variables for usc in macro expansions. because the symbol can be
typed in .. Also, gentemp will leave some infonnation around so that code analyzers or
the compiler can see that the variable is a generated variable so may . be optimized away
without loss of debugging infonnation. (Nonnal1y such a test would be that the symbol is
not interned. i.e .. it was created by gensym or copy-symbol. lbis does not work for
gentemp because gentemp interns the symbol so it can be typed in for debugging.) In
1'11... gentemp-crcatcd symbols are flagged by having a non-null si:gentemp-marker
property.
symbol-package symbol
This returns the "home package" of symbol, or nil if symbol does not have one (it is not
interned).
MC:NILMAN:SYMBOL 30
23-DEC-83
. .... ...• ~ ,.

a
The Value and FunctiunCeHs 68 Nil. Manual
9.4 The Value and Function Cells
See also chapter 3. page 11 k)r discussion about scope. extent. and binding. and chapter 3.
page 11 for a description of the NIL internal mechanism for performing variable and function
binding.
Special implementation qualification: because of the hairy value cell mechanism in NIL. value
cells arc not just allocated in the heap. so (due to lack of code to do some relocation right now)
there is an assembly-timc timi~ltjon on how many may he cremed. Thus, generating symbols and
using the valuc cells to store things may not work as . well as you expected (an error complaining
NEW_SLINK wants to grow the SLINK occurs). This limil4ltioll is nol a function of the
mechanism but rather of the Im:k of garb.lge-collccior. however.
symbo l-V8 1 ue symbol
Returns the current dynamic (special) vaJucof symbol.
symbol-value may be used with setf.
boundp symbol
Returns t if symbol has a defined dynamic (special) value, nil otherwise. Note that
(setq *foo* 1) => 1
(let «.foo. 3»
(declare (special .foo.»
(makunbound '.foo*)
(boundp '*foo*»
=> nil
=> 1
makunbound symbol
"Undefines" the current dynamic value of symbol.
An error is signalled if symbol is a constant (as defined by defconstant).
symbol-function symbol
Returns the current dynamic (special) function value of symbol. The result of symbolfunction
on a symbol defined as a macro or special fonn is undefined in COMMON LISP.
In NIL. special fonn definitions are not stored here, but other kinds of function
definitions are.
symbol-function may be used with setf.
fboundp symbol
Returns t if symbol has a defined dynamic function value, nil otherwise. (Like boundp.)
fmakunbound symbol
Analogous to· makunbound.
MC:NILMAN;SYMBOL 30
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••
Nil. Manual 69 Additional Names
9.5 Additional Names
Some other MACLlSP-compatibJe. LISP MACJlJI':E LIsP-compatible, and older NIL-compatible
names.
symeval symbol
Same as symbol-value, page 68.
set symbol value .
Same as (setf (symbol-value symbol) value).
fsymeval symbol
Same as symbol-function. page 68.
fset ,symbol fUllc/ion
Same as (setf (symbol-function symbol) function).
~ u t - P name symbol
Same as symbol-name. page 66.
P 11 st symbol
Same as symbol-pJist. page 65. Note that this is not exactly the same as the MACLISP
plist function (maybe it should be made to be?). The MACUSP plist function "works" on
disembodied property lists (specifically. it takes the cdr of a list) - this is sort of an
artifact of the MACLISP implementation.
setp 11 st symbol new-plisl
The same as (setf (symbol-plist· symbol) new-pUst).
qualifications hold as for plist.
The same MACLlSP-compatibility
get 1 symbol indicator-list
Standard MACLISP getf. Returns the subpart of the property list of symbol beginning with
the first indicator found in the list indicator-Ust, or nil if none was found. As in
MACLlSP, symbol may also be a disembodied property list. Essentially, this is the third
value returned by
(get-properties
(if (symbolp symbol) (symbol-plist symbol) (cdr symbol»
indicator-list)
copysymbol symbol &optional copy-props
MACLISP name for copy-symbol (page 66). Note that in MACUSP, however, copy-props
is a required argument.
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Symbol COllcalcntalion
9.6 Symbol Concatentation
70
NIL Manual
'Ibc following routines are not defined· by COMMON IJSP. but arc fairly useful in lIteir own
right by macros etc.
symbo 1 conc &rest frobs
symbolconc returns a new symbol (interned in lite current package) whose name is lite
concatenation of lite names of frobs. Typically. each frob is a symbol. however
symbolconc also allows it to be a fixnum (in which case its dccim.1I printed
represcntation is usro). a sIring. or a character (which must be convertihle 10 a string.
i.c .. satisty string-char-p).
sf: package- symbo 1 conc /'f.J('kagr-sp('C' &rcs( frobs
Simii

--
._-_.-..
-_._----------------------
N II. Manual 71 Numbers
10. Numbers
10.1 Types" Contagion, Coercion, and Confusion
10.1.1 The Types
Nn. provides several different representations for numbers. It provides integers. of essentially
unlimited precision. and floating-point. There is also the ratio data type. for representing noninteger
rational numhers. The complex daw type has heen added. but may not yet be
trustworthy for anything other than simple arithmetic operations. and has not yet been specialized
to a point where any significant "crunch" might be performed on it.
NIL integers arc currently of two kinds. There arc jixllulIlS and bignulIls . . Fixl1ums have 30
hits of precision. inc1uding the sign. and arc represented without cnnsing (i.e.. no memory
consumption). Integers which reqL'ire more ~an 30 bits to represent are implemented as bignums.
lJigllUII1S arc an extended data-type. and can grow to any size, limited only by whate\er system
parameter happens to be limiting the growth of your NIl .• and your patience.
There arc four primitive floating-point fonnats supported in NIL, as described in section 2.1,
page 3. These are
short-float
This is implemented as a single-float (VAX f _ f loa t format) with some of the fraction
bits tnmcated. so that it can fit into a !\IL pointer without any memory consumption. An
operations on this type essentially convert it to a single-float to perform the operation. and
then pack it back (truncating some of the fraction bits) when it is returned. 5 of the
fraction bil~ get truncated. leaving 19. or about 5 decimal digits of precision. Because the
exponent is the same as for single-float. it has close to the same range. however.
single-float
This corresponds to the VAX f _ float format; this provides 24 bits of precision (about 7
decimal digits), and a range of about 2.ge-39 to l.7e+ 38.
double - float
This utilizes the VAX d_float format. which has 56 bits of precision (about 16 decimal
digits). The exponent fonnat is identical to that of single-float, so the range _ is
essentially the same.
long-float
This utilizes the VAX h_float fonnat. This has a whopping 113 bits of precision (33
decimal digits), and binary exponent range from -16383 to + 16383. This is a range of
about 8.4e-4933 to 5.ge+4931. Because the machine instructions which operate on this
format of float are not supponed by all VAX hardware. NIL makes use of a VMs-supplied
condition handler to cause emulation of the missing instructions. As a compromise. it also
tries to avoid such instructions when it can (for instance, just for data movement).
MC:NILMAN:NUMBER 70
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Types. Contagion. Coercion, and Confusion 72 NIL Manual
10.1.2 Contagion and Coercion
Most of the NIL arithmetic functions are gelleric. rlbat is.. they accept numbers of any type
(subject to the semantics of the functiun. of course). and automatically "coerce" as necessary
when there are mixed types. Coercion is mainly a function of the floating-point types. For
instance. division of integcrs might yie1d a ratio:
(I 2 3) => 2/3
Howcver. rational numbcrs are always ·'normalizcd". and automatically "convert" back to intcgers:
(+ 1/3 2/3) => 1
When a flo,ning-point numher mcct~ an integer or a floating~ptlint numbcr uf a "shorter" type.
the latter is cOIn crtcd autumatically to thc format of thc .ftlftTIer bcfore thc operation procccds:
(. 2 2.0s0) => ~.OsD
(. 2 2.0dO 2.050) => 8.0dO
Such coinagiolls convcrsion is ncvcr performed in the othcr direction: floating point numbcrs arc
ne\cr COll\'crtcd to integers just because the rcsult might bc intcgral. for cxamplc. or ttl a shortcr
forr< at of float.
Complex numbers in Nil. are restricted to having components which are either both rational.
or both floats of the same format. A complex number with rational components will automatically
be converted back to a rational (non-complex) number if the result of a computation gives a zero
imaginary part. This never occurs if the components are· floats:
(. Nc(O 1) Nc(O I)} => -1
(. Nc(O.O 1.0) Nc(O.O 1.0» => Nc(-I.O 0.0)
J 0.1.3 Confusion
As was described in section 2.1. page 3. the fonnat of a floating-point number may be
selected by use of a particular character as the exponent specifier. 'Ibus; 2.0s0 is short-float,
2.0fO is single-float. 2.OdO is double-float, and 2.010 is long-float. COMMON uSPspecifies
that the default fonnat is Single-float. 'Ibis is the fonnat which is used when a floating-point
number is read in. and either no exponent character is used, or one of e is used (e.g., 2.5gel 0).
This is also the format specified as being returned by exponential. transcendental, or irrational
functions when given rational inputs. NIL has historically had a default (in fact, it used to be the
only) format of double-float. Becausc single-float (and shon and long) are all quite new to NIL,
the default format is still double -float. That is. currently
(typep 2.59 'double-float) => t
(typep (log 3/4) 'double-float) -> t
However. Ihis will be changed. The NIL reader/printer combination has been twiddlcd somewhat
so that while the default fonnat chosen by read is double-float, the printer will always print
the exponent character which will force the fonnaL
*read-default-tloat-tormat-
Variable
This variable (which is defined by COMMON USP) names the type of float which read
should create when it encounters one which does not specify the format. It should have
as its value short-float. single-float. double-float. or long-float. The COMMON LISP
default for this. is single-float.
MC:NII.MAN;NUMBER 70
23-DEC-83

a
. .
.... .. , ~(::ll;'~.:~j;i~~:~ ... ·3iL,·~L·;:~~iti~:';' .
NIL Manual 73 Predicates on Numbers
As a special interim hack. !'Il. allows this variable to have nil as its value. This is taken
to mean (to the reader) to produce double-float by default. but (to the printer) to not
usc an "unspecified" fonnat on output. That is. with .read-default-float-format* being
nil. the prir~ter will never produce "1.0", but rather "1.OdO".
It is strongly recommended that explicit usc ()f coercion (using the float function, page 78) be
made wherever the type of the result might matter. when using functions which must convcrt into
floating-point befi)rc procceding. This includes things like log sin. and sqrt. Note also that
certain operations on complex numhers with rational components. such as abs. implicitly usc
these other functions: for instancc.
(abs #c(3 4)) => 5.0dO
10.2 Predicates on Nunlbers
Note also the type predicates numberp. bignump. integerp. fixnump. floatp. ratiop.
rationalp. and complexp.
zerop number
Returns t if number is intcger, floating-point. or complcx lero. nil otherwise.
P 1 usp nOll-complex-number
m1 nusp non-complex-number
Return t if non-complex-number is of the appropriate sign. nil otherwise.
oddp integer
evenp integer
Return t if integer is odd (even), nil otherwise.
In NIL (but 1101 COMMON USP), oddp and evenp have been extended to gaussian integers.
evenp is defined as divisibility by 1 + i. and oddp as being not evenp. This definition
has the propeny that exactly half of the gaussian integers are odd and half are even.
While there is a remote possibility that this definition will be changed, I consider it very
unlikely.
10.3 Comparisons on Numbers
• number &rest more-numbers
/- number &rest more-numbers
< number &rest more-numbers
> number &rest more-numbe1'$
- number &rest more-numbers
Thcse functions each take one or more arguments. If the scqucnce of arguments satisfies
a cenain condition:
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Arithmetic Operiltions 74 NIL Manual
= an the same
I = aU different
< monotonically increasing
> monotonically decreasing
= monotonicaJIy nonincreasing
then the predicate is· true, and otherwise is false.
Complex numhers arc only acceptable as arguments to = and / =: the others require
their arguments to be non-complex.
These functions also h4t\"e fixJlum-only and duuble-fioat-only versions.
greaterp 1111111/
I1UlII} & rest more-lJumbers
.1 as s p IIUfIiI ,lIum2 &rest more-l1umbers
These are implemented as synonyms of < and >. and exist for MACI.ISP compatibility.
ma.': number &rest more-llumbers
m1 a I1l1l11be,. &rest morc-numbers
Generic max/min. Works on any non-complex numbers. Note also the existence of
max& and min& (page 87), which only work on fixnums, and max$ and min$ (page 91),
which only work ondouble-ftoats.
10.4 Arithmetic Operations
+ & rest numbers
plus & rest numbers
Returns the sum of all of the numbers. pcrfilrming type coercion as appropriate. If there
are no numbers. 0 is returned. The name plus is retained for MACLlSP compatibility.
Note also the fixnum-only + &, and double-float-only + $.
1+
addl number
( P 1 us number 1)
The nameaddl is retained primarily for MACLISP compatibility.
- number &rcst numbers
With one argument. - returns the negative of that argument. With more than one
argumcn~ it subtracts all of the others from the first. Type coercion is performed as
necessary. Note also the fixnum-only -a. and double-float-only -$ functions.
d1 fference number &rest numbers
When given more than one argument. difference subtracts from the first argument all the
others. and returns lhe result \Vhen given one argument. difference returns it. This is
noteworthy because it is compatible with the MACLISP difference function. and it is
illcompatible with - above.
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Nil, Manual
75
Arithmctic Operations
1- llumber
sub 1 number
(- number 1)
'Inc name sub1 is retained for MACLISP compatibility.
m1 nus number
This is the same as (- number): the name is retained for MACI.ISP compatibility.
• & rest numbers
t 1mes &rest numbers
Rcturns the product of all of the numbcrs. coercing as appropriate. The identity filr this
opcr,ltion is 1. The name times is retaincd ftlr \1Al'I.ISP compatibility.
I I11lIl1ber &rest numbers
This is the generic rationalizing division function. With one argument. / reciprocates the
argument: with more than one. it divides the first by all the others. and returns the
resull. / will return a ratio if the mathe1T!:\tical quotient of two integers is not an eX:lct
integer: truncming integer division is pel f(lnned by the ~1AC'l.lSP compatible quotient
function. and variolls sorts of truncation and rounding (not limitcd to fio,lting-point
input"') arc provided by the floor. ceiling. truncate. and round functions (section 10.7,
page 79).
quot 1 ent number &rest more-numbers
Tn'" i" th(' MA.C'f ISP-('('mpatib!r quotient fun~tion. Wh~n g!ven more th.;!n ~~ne ~rgmnent.
quotient divides the first hy all the others. and returns the result. With one argument,
returns that argument.
If quotient is given integer arguments. it perfonns truncating division (see truncate. page
79). However, if any of the arguments are ratios. it will instead do rational division, like
I.
conjugate number
Returns the complex conjugate of number, which is number itself if number is not
complex.
gcd &rest integers
Returns the greatest common divisor of the integers. With no arguments. ged returns O.
In NIL. ged works on all gaussian integers. The result will always lie within the first
quadrant, or along the positive real axis.
1 cm integer &rcst more-integers
Returns the least common multiple of the integers.
Like gcd. lem in NIL works on all gaussian integers.
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I rrational and Transcendental Functions 76 NII~ Manual
10.5 Irration,l1 and Transcendental Functions
Remember that the functions in this scction which must perfbnn their operations in floating ..
point. will convert rational numbers to double-float currently. but to single-float in the future.
pi
Constallt
The value of this constant is pi. in the. longest floating-point fonnat available; in NJ~ this
is a long-float. To use a shoner fonnat of pl. for instance double-float. one should use
something like one of the fonns
(+ (float pi O.OdO) n)
( + (c 0 ere e pi' do u b 1 e-flo at) II}
to an)id hm'jng the value of pi cause coercion to 'long-float in your cumputatiuns. Uses
of both coerce and float like the above will be optimized by the compilerc into the
appropriilte value.
I f other similar constants arc added to NIL. thcy also will be in 10ng-fl()~1t
should be treated similarly.
fimnat. and
10.5.1 Exponential and Logarithmic Functions
8XP number
Returns e raised to the power number. where e is the base of the natural logarithms. If
lIumber is a float. the answer is computed and returned in the same fonnat: if it is
rational. it is first convcrtcd to double-float.
exp t base-number power-number
Returns base-number raised to the power power-Ilumber. If base-number is a rational
numher and the power-number is an integer. the calculation will be exact and the result
will be a rational number. Otherwise. the calculation devolves into fioating-point. and will
use a logarithmic computation if power-number is not an integer.
log number &optional base
Returns the logarithm of number in the base base. which defaults to e, the base of the
natural logarithms. lbe rules of contagious coercion apply here: number and base are
converted to the largest format of the two, unless both are rational. in which case they
are converted to double-float.
It is an error if number is zero, unless base is zero. in which case the log is taken to be
zero.
sqrt number
Returns the principaJ square root of number. If number is rational, it is converted to a
double-float first; sqrt in NIL never produces a rational number even if number might
have a rational square root. even though this is not disallowed by COMMON USP.
If number is a negative non-'complcx number. a complex number is returned.
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NIL Manual 77 Irrational and Transcendental Functions
1sqrt integer
Integer square-root: the argumentmllst be a non-negative integer. and t11e result is the
greatest integer less than or equal to the exact positive square root of the argument.
10.5.2 Trigonometric and Related Functions
abs number
Returns the absolute value of the argul!1ent. which may be any type of number.
When applied to the complex plane. abs returns the disL4mce of t11e point from the
origin. which is
(sqrt (+ (expt rea/pari 2) (expt imagpart 2»).
Thus. for complex numbers. the result will always he floating-point hecause t11ere is a
$qrt hidden away in the computation. Applications which require only cOll1paring
distances from the origin may use t11e aho,"e f(lrm without the sqrt operation~ this is
done. for instance. hy the internal code for ged of complex integers.
s 1 9 n um number
By definition.
(signum x) - (if (zerop x) x (I x (abs x»)
signum of an rational number will return -1, O. or 1 according to whether the number
is negative. zero. or positive. For a floating-point number. the result will be a floatingpoint
number of the same fonnat with. one of the mentioned three vllhles_
signum of a complex number is a complex number of the same phase but with unit
magnitude. As a result. it will always be a complex number with floating-point
components (see the discussion under abs, above).
sin radians
cos radians
tan radians
Standard trig functions. The number radians will be convened to a double-float if it is
rational. These accept complex arguments.
asin number
acos Ilumber
asin returns the arcsine of the argument, and acos the arccosine. The result is in
radians. number will be converted to a double-float first if it is rational; it may also be
complex.
Note that (asin -5), for instance, results in a complex answer.
atan y &optional x
Fairly standard arctangent
With one argument (which may be complex). the arctangent is returned: for a noncomplex
argument. the result is between -fl/2 and '!T12 (exclusive). More generally. the
following definition is used:
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Numeric Type Conversions 78 NIl. Manual
atan(z) = -j.log( (l+i-z)-sqrt( 1/(I+z"2»)
With two arguments. neither may be complex. . '111c arclangent of y / x is returned. and
the signs of y and x arc used to derive quadrant information. Also. x may be zero as
long as y is not lero. TIle result will be between -." (exclusive) and 11 (inclusive).
s 1 n h number
cosh number
tanh lIumber
Hyperoolic·sine. cosine. and tangent. number m4ty be complex.
as 1 nh IIlImber
aeash Ilumber
atanh lIumbi'r
Etc.
10.6 Numeric Type Conversions
float Ilumba &optionaI other
If olher is not supplied, then if number is a float of any type. it is returned: otherwise, it
is con\'crted to a float of the default fonnat. which is currently double-float. but will be
single-float in the future.
If ollirr is supplied. then it must bea floating-point number. Ilumber is convened to a
float of the same type. Thus.
(float iTob o.orO)
causes explicit conversion of frob to a single-float. Note that this will conven to a shoner
fi)nn41t also.
The NIL compiler contrives to recognize the cases where float is given a constant ()ther
argument. and caU special efficient routines for convening to the given type.
rat 1ona1 number
11lis converts number to . a rational number. If it is already rational. it is returned.
Otherwise, a rational number is computed corresponding to the precise representation of
the number. For instance,
(rational (float 7/11 D.OsO» => 333637/524288
It is always the case that for a floating-point number f,
(= (float (rational 1) 1) J) => t
rationalize number
]f number is rational, it is returned. Otherwise, the floating-point representation is taken
to be an approximation of a rational number, and that rational number is returned. For
instance.
(rationalize (float 7/11 O.OsO» => 7/11
rationalize is not the most efficient coercion routine around ...
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•
NIL Manual 19 Integer Conversion and Specialized Division
comp lex rea/parI &optional (imagpart 0)
This constructs a complex number with real part of rea/parI, and imaginary part of
imagparl. If rca/parI is rational and imagparl is either (integer) 0 or not supplied, then
the result is just rca/pari. because complex numbers with rational components and a zero
imaginary part automatically turn back. into rational (non-complex) numbers. If either
argument is floating-point. then both components will be converted to the longest floating
point fnnnat of the two. For instance,
(complex 5 3)
(complex 1/5 3.0dO)
(complex 2.510 0.750)
(complex 2)
(complex 2.0)
=>
=>
=>
=>
=>
IIc(5 3)
IIc(0.2dO 3.0dO)
#c(2.510 0.710)
2
IIc(2.0 0.0)
10.7 Integer Conversion and Specialized Division
truncate /lumber &optional divisor
t100r number &optionaJ divisor
ce 111 ng /lumber &oplion.ll divisor
round number &optional divisor
These functions serve two similar purposes. They may be used to convert from a fioatingpoint
number to an integer in various useful ways, and they can also perfonn
division/remainder operations similarly.
If only one argument is given. it is converted to an integer by the appropriate method:
by truncation for truncate, by rounding towards negative infinity for floor, by rounding
towards positive infinity for ceiling. or by rounding towards the nearest integer for round.
(The NIL. and (,OMMO~ LISP round will round an exact half by rounding towards the even
integer: in this it may differ from rounding in other languages.) Two values are retunled:
the first is the result of the conversion, and the second is the remainder for the operation.
If number is an integer. then the first value is that integer and the second is O. If it is a
ratio. then the second will also be a ratio, and if it is a float, then the second will bea
float of the same fonnat. For example,
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(truncate 2.5) => {2, D.5}
(truncate 5/2) => {Z. lIZ}
(truncate -Z.5) => {-2. -O.5}
(truncate -5/2) => {-Z, -lIZ}
(ceiling 2.5) => {3. -0.5}
(ceiling 5/2) => {3, -I/2}
(ceiling -2.5) => {-Z, -O.5}
(ceiling -5/2) => {-2, -1/2}
(floor 2.5) => {2.·0.5}
(floor 5/2) => {2. 1/2}
(floor -Z.5) => {-3. 0.5}
(floor ,-5/2) => {-3. lIZ}
(round 2.5) => {2. 0.5}
(round -Z.5) => {-Z, -O.5}
(round Z.6) => {3. -O.4}
(round -2.6) => {-3, 0.4)
(round 3.5) =>' {4. -0.5)
(round -3.5) => {-4, O.5}
If the divisor argument is given .. the first value is the result of integer conversion of the
result of dividing /lumber by divisor, after the appropriate type of rounding or truncation
is performed. The second value is the remainder for that division after the
rounding/truncation. That is. if the values arc q and r. then
{:; nUlI/otlr (T i- q divisor) r) j => t
For instance~
(truncate 5 2)
(truncate -5 2)
(truncate 5 -2)
(truncate -5 -2)
(floor 5 2)
(floor -5 2)
(floor 5 -2)
(floor -5 -2)
=>
=>
=>
->
=>
->
->
=>
{2,
{-2.
{-2.
{2.
{2.
{-3.
{-3 t
{2,
I}
-I}
I}
-I}
I}
I}
-I}
-I}
What this means is. if truncate is given two integer arguments. then the two values are
the quotient and remainder. as obtained by those functions. If floor is given two integer
arguments. then the second value is the standard mod (page 81).
rem number divisor
When rem is given integer arguments. it is identical to the MACLISP remainder function.
More generalJy. however. it perfonns the truncate operation on its two arguments, and
returns the second value from that as its value.
rema 1 n de r number divisor
This is identical to rem. The name is retained for MAClISP compatihility: if number and
dil'isor arc both integers (which is aU the MACl.ISP remainder function accept~). then the
op~ralion is the same.
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Nil. Manual 81 l.ogicaJ Operations on N urn hers
One slight discrepency exists with the MACl.ISP remainder function: in MAC"I lSI>'
remainder wiJ] accept a Jil'isor argument of 0 and return number. This is incompatible
with the definition of rem (and also with fixnum open-compilation of remainder in
MACl.ISJ>!) because of the implicit division involved-in NIL, a divisor of 0 results in a
division-by-zero error.
mod number divisor
When Ilumber and divisor are both integers, then mod is the stmdard "modulus" function.
More generally. mod perf0l111S the floor operation on its two arguments, and returns the
second value from that as its value.
Note that by \'irtue of its definition in terms of floor which is a kind of division. a
divisor of zero results in a division-by-zero error.
ffloor Ilumber &optional divisor
ftruncate Ilumber &optional divisor
fee 111 ng I1wllber &optional divisor
fround Ilumber &optional divisor
These functions behavc just like floor. truncate. ceiling, and round. except that the first
value returned is converted to a float if it is not. While this is fairly useless for rational
arguments. it can rcsult in some efficiency gain for arguments of type float. Note that if
both arguments are rational. only the first value will be a double-float, not the second.
10.8 Logical Operations on Nuntbers
The logical operations in this section treat integers as if they were represented in two'scomplement
notation.
One common use of integers in this manner is as sets; each bit which is "on" (is 1) in the
integer represents the presence of a particular item in the set. If the integer is negative. then it is
an infinite set. because the sign is vinually extended to infinity. The presence of a particular item
in a set can be tested for with logbitp; one refers to the item by its lero-origined bit index.
Other set operations can be perfonned with the various boolean functions: log and performs
intersection, logior performs union, logxor performs set-exclusive-or, and logandc2 performs
set-difference. A new set with an item represented by bit-index index added can be constructed
by a form like
(dpb 1 (byte 1 index) integer)
10gb1tp index integer
logbitp is true if the bit in integer whose index is index (that is, its weight is (expt 2
index» is a one-bit; otherwise, it is false.
1 og 1 0 r &rest integers
logxor &rest illtegers
10gand &rest illtegers
logeqv &rest integers
These return the bit-wise logical inclusive or, exclusive or, and, or equivalence (also
known as exclusive 110r) of their arguments. ]f no arguments are given, the results are 0
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I #ogical Opcrations on Numbers 82 NIL Manual
for logior and logxor. and -1 f()r log and and logeqv. which are the identities for those
operations, Notc also t.he fixllum-unly versions of these. logior&. logxor&. logand&. and
logeQv& (page 88).
lognand integerl illteger}
lognor il/legerl integer2
logandcl integerl integer}
logandc2 il1Iegerl integer]
logorc1 ilJlrgt'rl integerl
1 ogorc2 iIlTt!~crl integer2
Th~se are the other six n()n·trivi~fl bit-wise logical operations on two arguments. Bec~luse
they arc not commutative or associative. they take exactly two arguments rather than any
number.
The "cl lt and "c2" in some of the above names should be read as "having complemented
argument 1 (ur 2)": for instance. logorc1 is the logical or of the logical complement of
illtcgerl. with ituegerl.
logandc1 and logandc2 are often used as bit-deuring functions. Howe\er. the ordering
given to such names as bit-clear or logelr is often confusing (and historically. has b~n
incompatible from one macro-package to another), togandc1 returns inTeger2 with aU bits
which are on in illlegerl. cleared; logandc2 returns integerl. after dearing any bits
which are set in illIeger2.
boo 1 e up inlegerl illteger2
'Jbe function boo'e takes an operation op and two integers. and retunlS an integer
produced by perfonning the logical operation specified by op on the two integers.
There are sixteen variables (the names of which are listed below) which have the boolean
functions as their values; the boolean functions are represented as fixnums from 0 to IS
(inclusive).
The NIL implementation of boole defines the boolean functions such that they map into
the standard "truth table" used in MACUSP. lbat is, if the binary representation of op is
abed. then the truth table for the boolean operation is
y
101
x
o I a c
I
1 I b d
For example, the boolean function 4 has binary representation 0100. This shows that the
result will have a bit set only when the corresponding bit of integer] is 1 and integer2 is
O. This is the logandc2 operation. New code, . especially that intended to betransponed
between COMMON LISI) implementations. should nel'er rely on this-this coincidence is
provided 01111' for M:\CLlSI' compatibility.
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...
Nil. Manual 83 I.ogical Operations on Numbers
Also for !\.1ACI.lSP compatibility. when Nil. boole receives more than three arguments. it
goes from left to right. thus:
(boole k x y z) (boole k (boole k x y) z)
In certain cases it may accept less than three arguments. Again. new code should not rely
on this behaviour.
lognot inleger
Returns the bit-wise logical 1101 of its argument. Every bit of the result is the complement
of the corresponding bit in the argument.
1 ogtes t illlcgcr/ int('g('r]
logtest is a predicate which is true if any of the bits designated hy the l's in ilJlrgerl arc
l's in integer 2.
(logtest x y) (not (zerop (logand x y»))
except that it can be done more efficiently. because it docs not have to actually compute
the logand.
ash intrger coUIll
Shifts in/('gcr arithmctically left by COUllt bit positions if COUllt is posltl\'e. or right -COUIlI
bit positions if cOUll1 is ncgative. The sign of the result is always the same as the sign of
integer.
The actual implementation of ash works on. and will produce. bignums. There is also an
A~hR n.1nftion which deals (In!y with fixnums.
In practice. COUllt is only allowed to be a fixnum ...
logcount i11leger
If integer is non-negative. logcount returns the number of "1" bits on in its twoscomplement
representation. If it is negative, then the number of "0" bits in that
representation is returned; this is then the same as the count of "Itt bits in the logical
complement of it
integer-length integer
integer-length returns the zero·origined index of the sign bit of the field needed to
represent integer in twos-complement notation. That is, any integer i may be represented
in twos-complement notation in a field (1 + (integer-length i» long. If integer is non·
negative, then it may be represented in unsigned binary fonn in a field (integer-length
integer) long. For instance,
(integer-length 5) => 3
because the binary representation of 5 is ... 0101.
The following two functions are provided for MACLISP compatibility. They both do some
semblance of manipulation of the binary representation of integers. However, the results of these
functions are defined in tenns of the absolute value of the integer they are examining-because in
Nil. integers are oriented towards manipulation of their twos·complement representation. these
routines may not be panicularly efficient on negative integers.
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t
Byte Manipulation Functions 84 Nil. Manual
haulong integer
Returns the number uf signific,mt bit~ in lheabsolule value of illteger. The precise
computltion performed is ceilillg(1og2(abs(illteger)+ 1».
For example:
(haulong 0) => 0
(haulong 3) => 2
(haulong 4) => 3
(haulong -7) => 3
haulong is provided ft'r MAfTISP c(}m~~ttibility:
prefer~nce.
. integer-length should be used in
ha 1 part integer COUIlI
This function exists primarily for MACI.lSP cumpatibility. Its functionality is subsumed by
the byte manipulation functions Idb and dpb. which are described in the following
section ..
haipart returns the high COUIlI bits of the binary representation of the absolute value of
integer. or the low -('mlllt bil~ if COUII( is negative.
10.9 Byte l\1anipulation Functions
There are various functions in NIL and CO!\'1 MO~ LISP to deal with arbitrary-width contiguous
fields of bite; within integers. These functions are not restricted to operations on fixnums. but
rather deal with the twos-complement representation of arbitrarily large integers.
Most of these functions use an object called a byte specifier. This object is used to refer to a
field within an integer. which is dctennined by the size of the field. and the' positioll of the field
within an integer. Both of these must be non-negative integers.
byte size position
byte constructs a byte specifier. You may not depend on the fonnat of the object
returned. only that it wi]) be acceptable for usc as a byte specifier by the fonowing
functions; in particular. the type of the object returned by byte may not be distinct. In
general. the restrictions on the magnitude of size and posilion are implementation
. dependent. In NIL, they may be any non-negative fixnums. Byte specifiers in which the
size and position will both fit in an unsigned field 15 bits long (that is. they are both
integers from 0 to 32767 inclusive) are represented more efficiently than others.
byte - size bylespec
byte-pos it ion bylespec
byte-size returns the size "component" of bylespec, and byte-position returns the
position "component".
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NIL Manual 85 Byte Manipulation Functions
1 db bytespec ill1eger
by/{'sl'('c specifics a field of integer to be extracted. That field extracted from the twoscomplement
binary representation of illlegrr is returned as a non-negative integer. For
instance. the low three bits can be extracted using the byte specifier constructed by (byte
3 0):
(ldb (byte 3 0) 15) => 7 :15is ... OlllIll in binary
( 1 db (byte 3 0) 14) => 6 ; 14 is ... 011Ill0 in binary
( 1 db (byte 3 0) -3) => 5 ;-4 is ...1111101 in binary
The third group of three bilS can he extracted lIsing tJ1C byte specifier (byte 3 6):
(ldb (byte 3 G) 15) => 0 :15is ... OOOOlll111inbinary
(ldb (byte 3 6) 63) => 7 :6Jis ... Olllll1111inhinary
(ldb (byte 3 6) -3) => 7 ;-3is ...lll1111101 in binary
Idb may be used with setf (page 38). if the fonn illfeger is a \'aJid 1'1£1('r argument to
'setf. Rather than modifying the integer itself. doing setf on a Idb fonn will "nest" like
( set f (1 db bytcspcc i11lrger) newbyte)
==>
(Sf.:c,;,f integer (dpb newbyte bytespec integer»
ldb-test bytespec integer
( 1 db - te S t bytespec integer)
(not (zerop (ldb bylespec integer»)
While a Idb -test can in general be . done more efficiently than the second filnn.
pr\ibat1y i5 not dl.HK ~f'Cddliy yet ii} j~iL
it
dpb newbyte bytespec integer
dpb is sort of the inverse of Idb. It returns an integer with the same binary
representation as illtrgrr. except that the field referred to by by1rspec is replaced by the
twos-complement binary represention of newbyte.
(dpb 3 (byte 3 0) 0) => 3
(dpb 7 (byte 3 0) 0) => 7
(dpb 0 (byte 3 0) -1) => -8
mask-field bycespec integer
This does not seem to be in yell
mask -field returns an integer whose binary representation is an zeros, except in the field
referred to by bylespec, which has the same bits as that field in integer. That is,
(mas k -f i e 1 d bytespec integer)
( d P b (1 db bytespec integer) bytespec 0)
(ash (1 db bytespec integer) (byte-pos ; ti on bytespec»
If the integer is being used as the representation of a set (section 10.8. page 81). then
mask-field could be considered to be perfonning an intersection operation on the set
represented by integer. and the set of all objects whose bit positions correspond to the
positions within the fic1d specified by bytespec.
MC:NILMAN:NUMBER 70
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R~andom Numbers
86 NIL Manual
de pos 1 t - f 1 e1 d 1I(' •...t~",e
This docs 110/ SCt'lIt 10 be ill ),el?
by/t'sp('c integer
This is the "inverse" of mask-fieJd. deposit-byte returns an integer which is the same
as inlcgcr, except that the field referred toby bylespec is contains instead the bYlespec
field of IJfwbyle. That is. it is like
(dpb (1 db bytespec newbyle) bylespec integer)
10.10 Random Numbers
random &optional modulus random-slale
I f no modulus argument is given. then this is compatible with the MAC'I.ISP. random
function of no arguments: it returns a number mndomly distributed over the range of all
fixnums. (CO\fMO;\ J IS}> docs not define random nfnn argumenL~.) Otherwise. the
answer returned by random is n number of the ~lme type evenly distributed between zero
(inclusive) and modulus (exclusive).
If random-slalc is supplied. it must be an object of type random-state: tIlis is what
holds the SUIte of the random number generator. If it is not supplied. then the global
random number SL'lte (the value of *random-state.) is used.
The random number returned is random over tta11 its bits": random-slale is used to
compute a sequence of random bilS which are used· to construct the result. For a floatingpoint
number. this is used as tile significand (fraction) of a constnlcted number which is
sc411cd to the appropriate range: filr an integer. a sequence of bit'i is constructed
approximately 10 bilS longer than that needed for the resul~ and then a modulus
operation performed.
*random-state*
Variable
This holds the global random state used by default by random. One may. for instance,
lambda-bind this variable to a new object of type random-state to save and restore the
state of the random number generator.
make-random-state &optional slate
This creates a new random-state object If slale is nil or not suppJied. then a copy of
the current value of *random-state* is returned. Ifs/ale is t. then a new random-state
is returned. seeded from the time. Otherwise, Slate should be a random-state; its state
is copied.
When NIL is first loaded up. the random-stale object in .random-state* is always in the
same state. It may be seeded from the current time by doing
(setq .random-state. (make-random-state t»
jf . that is necessary for applications. There is, however.. no official1y defined way to get a
"known" random-state from which the same sequence of pseudo-random numbers may be
generated. other than copying one withmake-random-state and saving it. If this is found to be
necessary (for instance to reproducibly debug a program which uses the random number
generator). the fonn
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NIL Manual 87 Fixnum-Onty Arithmetic
(si:make-random-state-internal)
wilt create a new random-state the same as the one i'\IL starts up with.
For MAC'USP compatibility, the random option to the status and sstatus macros is supported.
(status random) returns a copy of thc current value of .random-state-: (sstatus random
random-stale) restores .random-state- to a copy of that. Onc may also reseed by doing (sstatus
random integer).
10.11 Fixnum-Only Arithmetic
Currently. the :'\11. compiler does not make any usc of lype declarations to help it decide to
inline-code arithmetic routines. Primarily for this reason. !'IL provides a full complement of
fixllum-only and double-fioat-only arithmetic rOlltines. which will be in1ine-coded by the compiler
(when possible and reasonable) into fairly efficient code.
In Nil., as in MACIISP. the totally open-~ompi1ed fixnum-only routines behave "as the machine
docs": that is. overflow is generally not detected. Note that thc VAX hardware detects division by
zero. howcver. and those routines not compiled as machine instructions. sllch as "&. may detect
overflow and signa1 an crror.
10.11.1 Comparisons
-!r number &rcsl more-numbers
1-& number &rest more-numbers
& number &rest morc-numbers
< -& number &rest mcire-llumbers
>-& number &rest more-numbers·
Fixnum-only versions of the =. 1=.

Fixnum-Only Arithmetic 88
.& &rest fixllums
Fixnum-only multiplication.
1& fixllum &rest more-jixIlulIls
Fixnum-only division. With one ,lrgument. reciprocates. which seems singularly useless to
me~ since this is truncating division. reciprocation is an error if the argument is lero~ one
if it is one, otherwise zero.
\& jixlluml jixIlum2
Fixnum-only remainder. Although there is no CO\4MON I.ISP \ function to make the
fixllum-only (as inherited from MACI.JSP) \ function change incompatihly. the name of \
is heing changed to \& for consistency. Note that this function mllst nonnally he typed
in as \ \&. becallse \ is the "quoting" character in NH_
1+& ji.'Jmum
1-& jixllum
Fixnum-only "I + and 1 -.
ab $& jixflum
Fixnum-only abs.
s1gnum& jixnum
Fixnum-only signum.
"& jixllum I jixIlum2
Fixnum-only expt. It is an error for the result to exceed the range representable by a '
fixnum.
10.11.3 Bits and Bytes
logand& &rest fixnums
logior& &rest jixnums
logxor& &rcst jixnum
logeqv& &rcst jixnums
lognand& fixnuml jixnum2
lognor& jixllumJ fixnum2
logandcl& jixn:JmJ jixnum2
logandc2& jixllumJ jixIZum2
logorcl& jixllumJ fixnum2
logorc2& jixnumJ fixnum2
Fixnum-only boolean functions
boo 18& op jixnuml jixnum2
Fixnum-only boole.
MC:NILMAN:NUMBER 70
23-DEC-83
. . ;. , .' ~
~ . . ~ .~ ... ~ ~~
'~. ': " ~, : ,',,'" ,',,-."" . ."'.. '~'" "':" :,'::', '. '.~. .'~::"" '.,~", . ',.
' .~'

NIL Manual 89 Fixnum-Only Arithmetic
lognot& fixllum
Fixnum-only lognot.
logtest& fixl1uml fixIlum2
Fixtlum-only logtest.
logb1tp& index fixllum
Fixnum-only logbitp. 'Ibis is defined for an index larger than the number of bits in a
fixnum: however. inc/ex must he a fixnum.
as h& fixl1um COUllt
Fixnllm-only ash. Shifting hy a positive C()ulll may shift hil~ into the sign pOSItIOn, tJ1US
changing me sign of the result (and losing bits). It is an error if COUll I is not of type
(signed-byte 8). tJ,at is, between -128 and 127 inclusive.
logcount& fixllum
Not yet in?
haulong& jixl1ulll
Not inHne-coded. but provided for completeness (sec. perhaps. %fixnum-haulong. (notyet-written».
Maybe this should he diked. since haulong should dispatch just as rapidly.
1 db& bytcspcc fixllum
Fixnum-only Idb. This is not strictly a version of generic Idb which takes a fixnum
second argument. but ramer a version of low-level fixnum byte-extraction which takes a
general bytespec as an argument: it is an error for the byte to extend outside of the
fixnum (for the position plus the size of the bytespec to be greater than 30).
dpb& ncwby/e by/espcc fixllum
As Idb& is to Idb. so dpb& is to dpb. Other Idb& restrictions apply.
set -1 db& bylespec jixnum newbyte
Maybe this shouldn't be here, but it is in case setf gets used on Idb&.
Back in the olden days when there were few thoughts about integers greater than 34359738367
(or something like that), the byte-specifier to Idb and its friends used to be designated as ppss.
The interpretation of this is that. if you consider ppss to be a 4-digit oct~l number, the number
(octal) pp tells the position of the byte being referenced, and the ss the size. In order that a byte
specifier not be so restricted in the size of the "byte" it is referencing (since the pp can be
upwards-compatibly extended to the left but the ss cannot). NIL has incompatibly abandoned that
fonnat. So that code which uses this old fonnat may be trivially converted. however, the old
functionality may be obtained with the %Idb and %dpb functions. below.
Xl db ppss jixnum
Extracts the byte defined by ppss (as described above) from fixllum. It is an error if the
byte so referenced lies outside of the fixnum (that is, the size plus the position is greater
than 30).
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I )ouhle-Float-Only Arithmetic 90 NIL Manual
%dpb val PI'SS fi"lIlU1l1
Returns a fixnum which is firnulI1 with the byte defined hy ppSS replaced by the fixnum
val (truncated as necessary). It is an error if the byte so referenced lies olltside of the
fixnum (that is. the size plus tJ1C position is greater tJlan 30).
10.11.4 The Super-Primitives
Getting closer still to thc hardware ...
load-byte fixIIU1I1 POSiliol1 sizl'
This is thc primitive f'1I eXlract-a-byte-from-a-fixnum function. In the style of many ~II.
primitivcs. and in the style of the VAX byte-extracting instructions, it takcs arguments of
position and size (different ordering from the byte function). It is an error for the byte
dcscrib~d by posi/ioll and size to lie out of hounds of the internal reprcsentation of a
fixnum (30 bits).
depos i t-byte jiXIIUII1 P(}SIlIOII size llewbYIe
Modifics tJ1C byte. as per load-byte. Note argument ordering is different from dpb in
that I1l'wbyle comes last 'Ibis is to make it convenient fbr setf to usc.
sys :Xf1xnurn-plus-w1th-overflow-trapp1ng x y overflow-code ...
sys: Xf1xnum-d1 fference-w1 th-overfl ow-trapping
Special/onn
x y O\'erflow-code .•.
sys :Xf1xnum-t1mes-w1th-overflow-trapp1ng x Y Ol'crflow-code ...
sys : Xf 1xnum- as h -wi th-oYerflow-trapp 1 ng x )' ovclfloM/.codc ...
lbese are special fonns which primarily exist for the benefit of implementing generic
arithmetic functions. The appropriate binary operation on x and y, inJine-coded. is
pcrfonned: jf afterwards mere has been no o\'erflow, that result is returned. Otherwise,
ol'erflo~code is run, and the resultant value returned.
Only the compiler knows how to use these right now.
10.12 Double-Float-Only Arithmetic
NIL provides some functions (like those in MACLISP) which operate only on double-floats. It is
unlikely that corresponding functions wi]) be provided for other floating-point types when thcy are
added, however; inJine-codcd arithmetic on such numbers will be handlcd by declarations to the
compiler eventually.
+$ &rest double-floats
• $ &rest double-floats
-$ double-float &rcst more-double-floats
IS double-float & rest more-double-floats
1+$ double-floQt
1-$ double-floal
Double-float-only stuff. Essentially this is maclisp-compatible.
MC:NILMAN;NUMHER 70
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•
NIL Manual 91 Decompusition of FloalingPoint Numbers
abs$ double-float
l)ouble-Hoat-onty abs.
max$ &rest double-floats
mi n$ &rest duuble-floots
... s double-float jixl1um
The double-fimlt only exponentiation function.
10.13 Decomposition of Floating Point Numbers
All of the following routines are defined by CO\IMON LISP. The basic premise is that a
floating point numheris represented by some number of digits in a base b. multiplied by b to
some exponent. with a sign. In NIL on the VAX. b is of c()urse2 for the primithc floating-point
data types. so the exponent is a binary exponent.
float-radix float
This returns the radix b of float. For the I'll. prllnltlve float daL1 types (short-float.
single-float. double-float. and long-float). it always returns 2.
decode-float float
This function returns three values:
(I) 'Ibc sigllijicalld of floal. This is· a number between 1/ b (inclusive) and 1
(exclusive). which represents the bits of .POOI. The sole exception is for zero. for
which the returned significand is l.ern (of the ~1me floating-point type as floa!).
(2) The exponent of float. This is· an integer which. jf used to scale thc significand
(using scale-float. bclow), will produce a number with the same absolute value
as float.
(3) The sign of float; this is either 1.0 or -1.0, in the same floating-point fonnat as
float.
Thus.
(multiple-value-bind (significand exponent sign)
(decode-float float)
{= float (* (scale-float significand exponent) sign»)
=> t
scale-float float integer
This is like doing
(. float (expt b integer»
where b is the radix of float. It is done, of course. somewhat more efficiently and
without danger of any son of intennediate overflow or underflow if the final rcsultcan be
represented. It is an error if the final result cannot be represented; scale-float will signal
an error. (In a future NIL with a smaner compiler and type declarations, however, it may
be the case that open-compilation of this function will not signal an error.)
1n05e familiar with the PDPIO MACLISP fsc function will recognize this as being somewhat
of the same thing, although it is not subject to the kludges that fsc is (partly because the
VAX docs not represent unnonnalized floating point numbel'$} ..
MC:NILMAN;NUMRER 70
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,; ~:..-
Implementation Constants 92 Nil. Manual
float-sign float &optional other
If other is not supplied. then this returns the sign of float. 1;0 or -1.0. in the same
fonnat as float. This is the same as the third value returned by decode-float.
If alher is supplied. then the effcct is of transfering the sign of floal to other; the result
will be of the same floating-point format and absolute value as oliler. but have the same
sign as floal.
float-digits floal
This returns the number of base b digits in the representation of flaa/. In ~II.. this is a
conswnt for any particular one of the primitive floating-point lypes. Specifically. shortfloat
has 19. single-float has 24. double-float has 56, and long-float has 128.
float-precision floal
This (he said while looking the other way) is the same as float-digits except that it
returns 0 for zero.
1ntagar-decoda-float float
This returns three values. like decode-float. The difference is that the significand is
returned as an integer, and the exponent differs accordingly. The magnitude of the
integer is such that it is between "2"p (exclusive), and 2 .... (p-1) (inclusive), wherep is the
precision of float (as would be returned by float-precision). If the float radix is 2 as it is
for the NIL primitive floating types. then the integer will have the same number of bits
(intAgAr-IAnnth l';le(' 8) ~~ the rr{'d~ilJn. Again. an ~xccption for zero exists: the first
value will then be O.
10.14 Implementation Constants
most-positive-f1xnum
Cons~nt
most-negat1ve-fixnum
Constant
lbese have as their values the most positive and negative fixnums representable in NIL;
integers of the same sign but greater magnitudes have to be represented as bignums.
Because NIL uses twos-complement representation for fixnums, the absolute value of
most-negative-fixnum is one greater than most-positive-fixnum.
most-pos it iva-short-float
Constant
most-pos it ive-s1 ngle-float
Conslant
most-pos it i ve-doubla-fl oat
Constant
most-pos it iva-long-float
Constant
These have as their values the most positive numbers of the corresponding fonnats which
can be represented.
most-negat i ve-short-fl oat
Constant
most-negat 1ve-si ngle-float
ConstGnt
most-nagat iva-double-fl oat
'Constanl
most-nagat iva-long-float
COllslant
lbcse have as their values the most negative numbers of the corresponding fonnats which
can be represented.
MC:NILMAN;NUM8ER 70
23-DEC-83
.. t -,.-c,... ~ • .... ......... ".4...... •
~~» ~ ~~-: ~-~~~~ ?- ~ ~. ~
"- ~ - ... ~ .'"

as
NIl. Manual 93 Implementation Constant')
18ast-pos 1 t 1ve-short-float COllslall1
1 east-pos 1 t 1 ve-s 1 ng1 e-f1 oat C0I1Slall1
1 east-pos 1 t 1 ve-doubl e-float COllslall1
least-pos it ive-long-float
COllslall1
These have as their \'alues the smallest numbers of the corresponding fonnats that can be
represented. which are still positive.
least-negative-short-float
least-negative-single-float
least-negative-double-float
least-negative-long-float
These have as their\'alues
corresponding fonnats.
COIISlanl
COllslall1
COIlSltlnl
COllslall1
the most positive negati\'e numbers representable in the
short-float-epsilon
single-float-epsilon
double-float-eps1l~n
long-float-epsilon
These have as their values the smallest positive numbers which.
corresponding fannat. produce a different answer.
COI1Slanl
COllslall1
ConSlant
COllslanl
when added to 1.0 of thr
short-float-negat1ve-eps11on
single-float-negat1ve-eps11on
dQuble~floet-neg~t1ve-ep~1'on
long-float-negative-eps11on
These arc broKen and wrong.
Constant
('onstanl
r_ .... _"' .........
\,.. VIl.lIU'"
COllslanl
tvtC:NILMAN:NUMBER 70
23-DEC-83
, , ~ ~ -
. ,', . , :... .' :', . ';c ,-(: ',,: .> ,:;:~~~;;~~>',:-_: r~:'-, ":-, ....:;..:.

Characters 94 NIL Manual
11. Characters
In NIL. characters are represented as a separate data type. This provides multiple benefits;
among them. the object maintains some semantic identity when it appears in code (it is obvious
that it is a "character"). and since it does maintain its identity as a character. the read/print/read
"fixed-point" is capable of functioning across differing LISP implementations that internally utilize
different character sets (e.g.• ASC'II VS. EBCDIC).
Characters in NIL have three different attributes: their code. their bils. and their [0111. 'Ibe
code defines the basic ("root") chamcter. The bit"i are used as modifiers. Typical1y. an input
processor (such as the editor, or even the prescan for the tople\'c1 Lisp read-eval-print loop) will
treat a character without any bits as "ordinary" and assume it is part of the text being typed in.
but treat a character with some bits, as being a command. Four of the special bits are named:
they are control, meta. super. and hyper. The font of the character defines how certain things
about the character arc defined: for instance. equating characters of different fonts (char-equal).
whether a character is upper or lower case. alphabetic. or a digit (upper-case-p etc.). and how
to do case conversion (char-upcase). While NIl.' docs not yet rcally define "fonts", there is a
mechanism for how such definitions can interface to the low-level character manipulation
primitives which utilize such things (section 11.7. page 100).
NIL character objects are immediate-pointer structures; they require no storage. Most of the
routines which construct, dissect. and compare characters are open-coded by the compiler.
Thc ~~lL character sct ha5 not y~t b~cn ck,iil~d up with respect tu -the cUllru~iulI UCLWCCIl Uu:
ASCII control characters and the characters it uses with the control bit See section 11.6. page 99.
char-code-l1m1 t
Constant
char-font-l1m1t
Constant
char-b1 ts-l1m1t
Constant
These variables have as their values the upper exclusive limits on those attributes of
characters. The values should not be changed. It happens that, in the VAX
implementation, all three are 256 so that each quantity will fit into an g"bit byte.
11.1 Predicates on Characters
standard-char-p character
This returns t if character is one of the "standard" ASCII characters. These are an the
ordinary graphic characters (alphanumerics and punctuation characters). plus Space and
Return. Only characters with 0 font and bits attributes can be standard.
graph 1 c-char-p character
Returns t if character is a graphic (printing) character; that is. it has a single glyph
representation. No character with non-zero bits attribute is graphic. Whether or not a
character is graphic depends on its font
MC:NILMAN;CHAR 33

NIL Manual
95 Predicates on Characters
alpha-char-p character
upper-case-p character
lowe r - ca s e - p character
both-case-p character
a1 phanumer 1 cp character
Predicates on character objects. All arc nil for characters with any bits; ()thcrwisc~
depend on the font.
thcy
char- character &rest more-characters
char( character &rest more-characters
char(- character &rest more-characters
char> character &rest more-characters
ch a r> - character &rest more-characters
charI- character &rest more-characters
These routines collate or compare characters. The comparison is depcndent on the bits,
fon4 and case of the characters. Each routine returns t if all pairwise combinations of its
arguments satisfy the appropriate predicate~ nil otherwise; if a single argument is givcn,
the result is t.
char = is the primitiv~ function for tclling if the characters are "thc same charactcr"-that
is, if their code, bjts. and font arc all the samc. It is what is used by eql and equal for
comparing characters. char / = returns. t if none of the pairs of characters are char = .
ch~r =, =d cn:lr) cc!mtc t'1c eh~rnctcrs ~eeording to some unspecified
collating sequence. What is guaranteed is that the upper-casealphabetics, the lower-case
alphabetics, and the digits will not bc intcrspersed within thc coUating sequence, and,
within each of these sets, they follow the obvious coUating order.
char-equal character &rest more-characters
char-l essp character &rest more-characters
char-greaterp character &rest more-characters
c h a r - no t -1 e ssp characler &rest mor~characters
char-not-greaterp character &rest more-characters
These routines compare characters independently of font, bits. and case. This does not
mean that only the code portion of the characters is compared, but rather a fontdependent
canonicaHzation is performed on the characters before they are compared.
Thus, for two characters in different fonts, it is possible for them . to not be char-equal
even if they have the same code (one might be a "greek" character and the other
"roman"), and conversely it is possible for them to be the same even with different codes
(one might be upper-case and the other lower-case).
MC:NILMAN;CHAR 33
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Ch4lmcter Construction and Selection 96 NIL Manual
11.2 Character Construction and Selection
character jrobozz
Coerces jrobozz to a character. It may be a character. a fixnum. in which case char-int
is applied. or a string. symbol. or character vector of length 1. in which case that single
character is returned. This is what is used· by the coerce function (page 9).
char-code character
char-bits character
char-font character
These three functions extract those attributes (as fixnums).
by the compiler. and accept only character objccts.
AI) are efficiently open-coded
code-char code &optional (bils 0) (font 0)
Creates. a character with code, bits, and font of code. bils. and font. unless that is not
possible in the implementation. in which case nil is returned. In other words. it is an
error for code. bils. or fonl to not be. non-negative integers, however they need not be
less than char-code-limit, char-bits-limit. and char-font-limit respectively.
maKe-char char &optional (bitsO) (jontO)
Creates a character with code of the the code of char. and with bits and font of bils and
jont. unless that is not possible in the implementation, in which case nil is returned.
make-char could have been defined as
(dp.flln maIcA-r.har {t::"~r &optional (bits 0) (font 0»
(code-char (char-code char) bits font»
11.3 Character Conversions
char-upcase char
char-downcase char
Upper- or Jower-casify char, preserving the font and bits attributes of it. Note in
particular that these functions just return char if it has a non-zero bits attribute, because
such a character is not alphabetic and hence not subject to having its case changed.
char-i nt char
Returns a non-negative integer (in NIL. this will be a fixnum) encoding of the character
char. If the bits and font of char are 0, this is the same as char-code. This is useful
for hashing. and certain charactcr-fixnum conversions such as those needed for the
MACLISP tyi function are defined in tenns of char-int.
1nt-char integer
If there is some character c for which (char-int c) equals integer, that character is
returned; otherwise. nil is returned.
~1C:NII.MAN:CHAR 33
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NIL Manual 97 Internal Error Checking Routines
char-name char
Returns the name of the character char, if it has one. Supposedly. all characters which
have zero font and bit4i attributes and which are non .. graphic (see graphic-char-p) have
names.
In NIL. the name of a character is by convention a symbol in the keyword package.
name-char sym
The argument S)'111 must be a symbol. If the symbol is the name of a character object.
that object is returned: otherwise nil is returned.
In !'II. character name symhols arc symbols in the keyword p4lCk~lge.
d1git-char-p digit &oplional (radix 10)
digit-char-p is a semi-predicate. If digit, which must be a chanlcler, is a digit in radix
radix. then the weight of thm digit is returned. otherwise nil is returned. By definition. a
character with non-zero bits is not a digit. so for that digit-char-p will always return nil.
digit-char u'£'iglrl &optionaJ (radix 10) (fimf()
I f it is possible to construct a chilracter with the given bits and font which has the weight
weigh! in radix radix ~ then such a character isreturncd. otherwise nil is rcturned. weight
must be a \ alid weight for thc radix (a non-negativc integer less th,m radix). Note the
similarity to make-char (page 96) also.
(digit-char 5) => #\5
(digit-char 10) =~ nil
(digit-char 10 25) => #\A
Note that unlike make-char, digit-char does not take a bils argument. This is because
a character with a non-lero bits attribute is by definition not a digit.
11.4 Internal Error Checking Routines
The following may be of use to uscrs writing their own routines for dcaling with characters.
(They should eventually be supplanted by more general type-checking macros, which will probably
turn into calls to these routines ... )
s1: requ1 re-character character
Error.;checks that character is in fact a character. This is what is called by (for example)
the interpreted version of char-code.
s 1: requ1 re-character-f1xnum integer
Error-checks that illteger is in fact an integer for which there is a character representation:
that is, on whichint-char would return a character. All such intcgers in NIL happen to
be non-negative fixnums.
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I.ow-I.evel I nterf~lces 98 Nil. Manual
11.5 LOl\'·Level Interfaces
Xint-char fixllum
Non-check version of jnt-char. It is an error for fixllum to not be the integer encoding
of a valid character object. as would be returned by char-int.
The following four routines define digitness in the NIL character set. at a low level. These
routines do 1101 depend on the fillli of the character (if they take a character as an input); rather,
they dcfine thc basic conversions for the "standard" ~IJ. character set (~II"S interpretation of
ASCII).
% v a 11 d - dig 1 t - r ad 1 x - p radix
This defincs the valid rangc of radices which %digit;..char-in-radix opcratcs on. The
radix must he a fixnum.
%d1 g1 t-char-1 n - radix -p char radix
Primili\'c predicatc for testing whcther thc charactcr ohject char is a digit character in the
fixnum radix radix (which must be a valid numeric radix).
%digit-char-to-we1ght dwr
For any char which satisfies %digit-char-in-radix-p, this will return the weight of that
digit.
%d1g1t-we1ght-to-char weiRhl
This inverts %digit-char-to-weight.
The fonowing two routines perfonn low-level case mapping for the NIL character set
%char-upcase-code code
%char-downcase-code code
These routines perform low-level case mapping for the NIL character set code must be a
valid character code; the returned value is a character with 0 bits and font attributes.
For example. if NIL did not provide low-level support for multiple fonts,
(char-equal el e2)
would be the same as
(char= (%char-upcase-code (char-code el»
(%char-upcase-code (char-code el»)
The actual definition of char-equal is somewhat different in that the translation and
canonicalization of the characters depends on their font
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NIL Manual 99 The N II. Character Set
11.6 The NI L Character Set
As can be seen. the format of character objects in NIL provides for a basic eight-bit root
charactcr (defined by the code). which can then have both bils and fOllt attributes added to it.
However. the 1/0 devices l':ILmust deal with only handle (at most) eight-bit characters-often
only scven.
In principle, !\Il wilt utilize an eight-bit character set; half of these witl be graphic characters
(the normal ASCII graphics. plus special symbols), and the other half reserved. foonat effectors
(such as line feed. backspace), and special commands for things like the editor and debugger
(Aborl. Resume. C/eor".\'cr{'cll. that kind uf tJ'ling). All oftJ'lcse chamc(ers will then he ahlc to
have bils mld jiml allribu(es added.
To deal with tJlis on (for instance) an urdinary seven-bit ASCII tenninal. 'II will haye to do
mrce thil)gs in the future. These are not done now. but are noted because they have bearing un
me representation of character objects and input from devices.
I Turn ordinary ASCII con£rol charilcters into the ~II \ersion of the control character. For
instance. the :\sell character with code of 1. which is what you get when typin~ ('amm/­
A on a standard ASCII keyboard. will turn inw tJ1e character A (uppercase 1\) with the
COlltrol bit set.
2 Provide "prefix" character-Je\"el commands in variolls places in order U14lt other chanlctcrs
with bits may be entered (this is what is done in the editor). For instance. in the current
inpl1f rnl('('~"()r t'4;

Primili\'e Fonl I }cfinitions 100 NIL Manual
$ set term/eightbit
to (>Ct,.) Now we have a seven-bit character. If the seven-bit code is less than 32. and if it is not
one of the codes for Backspace. Tab. Lill efeed. or Return (8. 9. 10. and 13 respective1y). then
add 64 to it. and set the {olllro/ bit. Adding 64 fonns the corresponding uppercase-alphabetic or
punctuation character. Thus. 1 turns into {o1llro/-A (65 plus Control). and 135 turns' into
{vlllrv/-Afela-G (135 = 128 + 7. = A.Jela + CQllIro/ + 73 which is G).
11.7 Primitive Font Definitions
Thi\ section details how "fonts" are described at a low level in \11, in order to be interfaced
to the character primiti\'es described in this chapter. The contents of this section can he s,,'c1y
ignored by anyone who isn't going to try to define fonts and interf~lce them to !':IL.
first. remer:tber that the code portion of a character is exactly 8 bits.
There are several ttattributes" of a font which we need to encode in such a way that certain
operations become trh': al. They are these:
C(}Il\'crsioll 10 Ul'l'Cl case
('ol1\'crsieJl/ 10 !owe,..case
These want to be done rapidly
Icsling/or ('crlain alfribulcs
the predicates upper-case'-p. graphic-char-p. both~case-p. etc.
cOIllParison of charactcrs of d~(rere11l fOil IS
Two goals are desired here. It may be desirable for two characters in different fonts with
the same code to 1101 be char-equal. because they represent different things. It might
also be desirable for two characters in different fonts with different codes to be charequal-one
might be p. the other P.
gelling H'ciglils of digits
obtaining digit characters from weights
For efficiency. all of these goals are implemented through table lookup. There are several
special variables whose values are simple vectors which contain one entry for each possible font
(256 entries in each vector). In the initial NIL environment. all of the entries of each vector are
initialized to the same thing.·
Before these tables get listed, there are a couple of conventions which must be explained first
The first is what is caned internally a translation table for characters. 1bis is just a simple-string
or simple-bit-vector 256 bytes (2048 bits) )ong~ for doing code-to-code translation. For instance,
translation to upper-case for a particular font utilizes such a table. The NIL primitives are defined
such that it docs not matter whether this datastructure is a simple-bit-vector or a simple-string.
Another such datastructure is a sy1l1ax table. This is the same as a translation ciblc~ but each
byte within the table is treated instead as a bit-mask with one bit set for each attribute about the
code being defined. Both of these concepts will be abstracted away from characters in a' future
~JL
1be attributes about a font we define arc these:
uppr,..casc IransTalion lable
lowe,.case trallslalioll/able
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, . _', _ -. -' , .' • ~ c " ' ~ - , • '," - ,

NIL Manual 101 Primitivc Font Definitions
Etch font has one of each of these. ehar-upease works by returning a new character of
the same font. with a code which is the result of extracting the byte from the upper-case
translation table at the code index. (If the character has non-zero bits it is just returned
however.)
syntax table
A syntax table (as described above) with syntax bits for the character primitives graphieehar-p.
upper-ease-po lower-ease-p. both-ease-po alphanumeriep. and alphaehar-p.
Constants for these bits are defined below.
digit weight table
This is a simple vector 256 long with one entry for each character code. All entries are
fixnul11s. Those entries corresponding. to characters which cannot ever he interpreted as
digits should he -1: all others should have the weight of the digit.
digil cliar lable .
This is a simple-string (it must 1101 be a simple-bit-vector) used for conversion from a digit
. weight to thc corresponding character. The length of the string is the maximum radix
which 'can be handled in that font. and all entries in-between must be valid. For
iT: tance. in the standard such table. the entry at index 9 is the character 9. and the
entry at index 12 is the character C.
the 1)]J('Jilce
The fonnat of this object is not defined: the typefaces of different fonts are compared
with eq by such predicates as char-equal. This is discussed later.
Iypeface cGl1ol1icalizatiolltable
This is a simp]e vector 256 long. which is used to produce a canonicalil.ation of a
character within a typeface. The eiemenlli ot the vector are tlxllurns. When two characters
of the same typeface are compared. the code of each character is used as an index into
this table (there is one per font. remember), and that result is used for the comparison.
This allows a typeface to have. among several fonts. more than 256 characters.
s 1: nata-pr 1m1 t 1 va-fan t font-number &key upper-ease-translations syl1lax-table
lower-case-translations typeface backwards-reference digit-weight-table
digi I-chaT'" table t),peface-callonicalization
This assigns all of the infonnation described above to the font fOllt-number. Appropriate
defaults are assigned for those entries which are nil.
The following constants define syntax bits used in the syntax table used. For each, the uSv_tt
constant has as its value the position of the bit within the field (byte), and the "Sm_tt constant a
mask for testing the bit (with logtest&~ for instance) or setting it (with logior&).
s1: charsyntax$v_graph1c Constant
s 1: charsyntax$m_graph 1 c
Constant
This hit tells if the character is graphic; that is. if it should satisfy graphie-char-p.
s1: charsyntax$v_uppar _case Conslant
S 1: charsyntax$m_upper _case
Constanl
This bit tells if the character is upper case (should satisfy upper-case-p).
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Primitive Fonl Definitions
102
NIL Manual
s1:charsyntax$v_lower_case
s1:charsyntax$m_lower_case
This tells if the character is lower case.
{OIlSlant
ConSlallt
s1:charsyntax$v_both_caS8
s1:charsyntax$m_both_case .
This tells if the character satisfies both-case-p (page 95).
s1:charsyntax$v_d1g1t
s1:char5yntax$m_d1g1t
This teBs if the chamcter is Cl (decimal) digit chamcter.
COllstanl
Constant
COllslOllt
COils/alii
s1 : charsyntax$v_standard
('011.';/(1111
51: charsyntax$m_standard COIiSIGllt
This lells if thc character, were it if font O. is a s~1ndard char (standard-char-p. page
94).
s1: charsyntax$v_alpba COllsttlnt
51: charsyntax$m_alpba COllslall1
This tells if the chamcter is alphabetic. If the chiJracter is either upper or lowef case.
then it must have this bit set also. It is hypothctically possihle. however. for a character
to be alphabetic but neither upper Of lower case.
Character comparison ala char-equal. char~lessp. etc .. i~performed itS follows. w~ :lSSllme
thJt it is possible to group characters into logical "typefaces": canonicalil.ations within a typefllce
are valid. and comparisons of characters of different typefaces are not. Each font has associated
with it one such typeface. and the assumption. is that many different fonts map to just a few
typefaces. When two characters are compared. if their typefaces are the same. then the codes of
the characters are translated into fixnums by obtaining the eodeth clements of the typeface
canonicalization tables, and the results compared in the appropriate manner (= for char-equal, <
for char-Iessp, etc.). If the typefaces arc ·different. then the characters are not equal; for
ordering, they are compared in a manner consistent with char

NIL Manual 103 !\ITays
12. Arrays
Arrays in I'll _ encompass a large number of varied objects which share certain features and
aspects of usage. NIL arrays may range in rank (number of dimensions) from 0 to about 250. All
array indices in NIL are zero origined. One-dimensional arrays are veClors. are of the type vector,
and may be used by the various sequence functions (in chapter 7). Restrictions on the types of
the clements of an array (its elemenl IJpe) can result in special storage and access strategies. The
data in multidimensional arrays is always stored in row-major order; this is compatible with
MACI.ISP. although nonnally it docs not matter-.
12.1 Array Creation,! Access,! and Attributes
make - ar r 8y dimcllsilills &key el(,1I1(,III-I)1)C displaced-Io displa('('d-ind('x-ojfs('/ alfius/able
jill-poil1lcr
This is the general array creation function. dimensions may be an integer. in which case
the rank of the created array will he_ one (it will he a vector). or a list of integers which
are the sizes of the correspondhq dimensions of the array.
The array wi11 be created to hold objects of type ('/('melll-I)1)C. If this is not supplied. t is
assumed. and the created array will be able to hold any lisp objects. The most common
types. aside from t. are bit (which creates a bit-array). and string-char (which creates a
string-char-array). The special types which Jl'IL supports. and their consequences. arc
tii~"lIcc(\ti ..........-.-..,.......- ............ in c",.,inn _....".... 1"" "--;-4 "''tnt> 11\.1
.t'~C" .&.v ••
If jill-poilller is not null. then the array must be one-dimensional (a vector). It will be
created with a fill pointer initialized to jill-pointer. which must be between zero and the
size of the array (inclusive). Fill pointers arc discussed in section 12.3. page 105.
Nonnally, the size of an array may not be changed (other than by modification of its fill
pointer if it has one). This allows the implementation some leeway to provide for more
efficient access and storage. However, if adjustable is specified and not nil, then the array
will be created in such a way that its size (and its displacement attributes) can be
modified later by adjust-array. Modification of array size and attributes is discussed in
section 12.5. page 107.
The displaced-to and displaced-index-offset arguments control array displacement; that is
where one array can "point into" another. This is discussed in section 12.4. page 107.
are' array &rest indices
Returns the element of array addressed by the indices. The number of indices must
match the rank of the array, and each index must lie between zero (inclusive) and the
size of the corresponding dimension of the array (exclusive).
If the array is one dimensional (Le .• a vector) and has a fin pointer. the fill pointer is 110t
used to decide the range of the array which may be validly referenced: aref may be used
to access all clements of such an array. In this, it differs from elt (page 49).
MC:NILMAN;ARRAY 36
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Array Element Types 104 NIL Manu

-------------------------------
NIL Manual 105 FiJI Pointers
string-char
The array can only hold characters which satisfy the predicate string-char-p (page 19).
A one-dimensional array of this clement-type is of type string. A string that is not
adjustable, not displaced, and has no fin pointer is of the type simple-string: this is
implemented more efficiently than a more general string~ and can be efficiently accessed
with the schar function (page 114). Chapter 13 is devoted to strings.
character
The array can hold only characters (but they may be any type of characters). This
provides no advantage over the clement-type t in the current implementation: in a later
'II., vectors of clement-type character will he acceptahle to the string function~ (chapter
13).
(unsigned-byte 8)
(signed-byte 8)
(unsigned-byte 16)
(signed-byte 16)
Store those integers which arc representable in tl··~
respective fields.
double-float
The double-floats arc stored p,lCked in machine representation. Until lhe' compiler has
sufficient power to speciaJly handle accesses to arrays of this type, there is no particular
benefit to their usc. because a generic array reference to a dl.luhle-float array will have to
cons the number to return it.
t Au aIT"y \if dement-type t ean h\ild any lisp (}bjc~t. If sli~h dB eli"d), i~ um:-Jilm:lJ~iullai.
not adjustable. not displaced. and has no fill pointer. then it is a simple vector (of the
type simple-vector). Such a vector is especially efficient, and may be accessed with the
svref function (page 109).
12.3 Fin Pointers
The :fill-pointer option to make-array allows one to create a vector of varying length. It is
only applicable to one-dimensional arrays. The fill pointer of a vector is an integer which may
range from 0 to the size of the vector. 1t is used as the length of the vector; the value of the fill
pointer will be returned by length (page 49). and used as the length by all sequence and string
functions: in fact, by everything except for aref (and its variants such as char and bit). The
contents of the array at and beyond the fill pointer are still considered valid;· they just are not
considered when the array is viewed as a sequence.
A string with a fill pointer is reputed to be similar to a PL/I varying string. although such a
comparison is beyond the realm of this author's knowledge.
To find the actual allocated length of a vector which has a fill pointer, use array-dimension
with a dimension number of O. array-dimension always returns the al10catcd length.
f\·1C:NII.MAN:ARRA Y 36
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Fill Pointers 106 NIL Manual
array-has-f111-pofnter-p array
This returns t jf array has a fill pointer (implying that it is a vector). nil otherwise. It is
an error for array to not be an array.
fill-poi ntar vector
This returns the fill pointer of vector, which must bea vector with a fill pointer. " lnis
may be used with setf.
vector-push \JeClor object
reClor must be a vector with a fiU pointer. If the fiU pointer is a vaJid index into the
\ector (that is. its \".llue is J~ss than the allocated length of the ,"ector). then vector-push
SlOres (}/~i('('1 into thilt slot. incr~l1lents the fill poi Iller. .md re(Urns the original
(linincremented) fill pointer (which address~s where the uhject was stored). If the filt
pointer is the same as the allocaled length (the only other valid situation). then vectorpush
returns nil.
Note that the argument order to vector-push differs from that of the push macro (page
38). This will be incompatibly chmlged in the future. at which time ver.tor-push will
contrive to figure out which argument is which from their types.
vector-push-extand vector object &optional extension
This is like vector-push. but whereas vector-push will return nil if the vector is "fun",
vector-push-extend will instead can adjust-array to incre,lse the si7e of V('Clor in order
thilt if miehr no the:- pnli;h. Thu~, it nl?\'l~~ rt:tt!r!l~ niL If ~X{!>f?!f(lf? is 5upp1i{'d and not nU.
then that is the amount by which the size of \'eclor is incremented by adjust~array, if
necessary; otherwise. some random guess based on the current sizcis used.
In order for adjust-array to succeed in increasing the size of veclor. l'l'clor must have
been crealed with the :adjustable option to make-array; see section 12.5, page 107.
The ordering of the arguments vector and object will be reversed in the future; see
vector-push, above.
vector-pop vector
This is the inverse of vee/or-push. The fill pointer of vector is decremented, and the
object addressed by that index is returned. The fill pointer must not already be zero.
reset-fill-pointer vector &optional (illdexO)
Resets the fin pointer of veclor, which must have one. If index is not specified, 0 is
assumed.
This function is obsoleted by the use of fiU"pointer with setf.
One common use of vectors with fill pointers is as buffeTS. For example. the NIL compiler
lIses a vector with a fin pointer for anocating a tahle of value cell indices to be referenced by the
code it is compiling. It creates a vector with make-array. specifying that the array is adjustable,
mld gi\ ing it an initial fill pointer of O. Then. it uses vector-push-extend to add Cl new entry,
and the value thm returns is the index into this table. vector-push -extend takes care of
increasing the size of the vector jf the initial guess as to its size was too small.
MC~NII.M;\N:ARRAY 36

N II. Manual 107 Displaced Arrays
This same technique can be used for generating text. jf the vector is a string (that is. makearray
was given string-char as the :element-type keyword). This is how some string
accumulating primitives work.
With vector-pop, vectors with fill pointers can also be used as stacks.
12.4 Displaced Arrays
Arrays may be created which do not have data of their own. but in fact "share" data with
some other array. These arc displacrt/ arrays. The lIses for displaced arrays \·al'}'. One might
want to access the clements of a multi-dimensional array as if it were a \ ector: this could he
done by
(make-array size :displaced-to other-array)
which returns a vector which will "ccess the clements of Oilier-array in row-major-order. With
displacement. a displaced index offset may also be specified. Conceptually, when an array is
accessed. a single index is computed from the indices and dimensions of the array: this is the
index into the row-major-order data. This iildex then has the displaced-index-offset added to it.
to gel the index into the data for the array being displaced to.
Another potential use for displaced arrays is to reference some "substructure" of an array
which implicitly has some ·'structure". This causes modification of the displaced array to modify
the referenced subpart of the original array. In genera1. however. it is not appropriate to use
array displacement as a substitute for a subseq operation (page 50): it is intended fi1f cases
where modification of one must implicitly nl0dify the other. although if the subsequence is large
it may be worthwhile.
Efficiency note; displaced arrays which are displaced to non-adjustable arrays access at just
about the same speed as nonnal arrays (not counting those which are especially efficient. namely
simple vectors, simple strings, and simple bit vectors). Arrays displaced to adjustable arrays are a
touch slower. At this time. the l':IL compiler does not know how to inline code any non-vector
array access, however, so aref (or use of it with setf) will produce general function call unless
there is exactly one index.
12.5 Modifying Array Sizes and Characteristics
Nonnally, an array may not have the size of its dimensions or other attributes changed once
it is created (other than modification of its fill pointer; section 12.3, page 105). If a non-null
:adjustable option is given to make-array, however, the array will be created such that this is
possible.
·adjust-array array dimensions &key displaced-to displaced-index-offset element-type
jill-pointer
adjust-array interprets dimellsio11s just as make-array docs. The array is modified to
have the new dimensions; however. its rank may not be changed.
If jill-pointer is specified. then array must have originally been created with a fill pointer:
the value of ftll-poilller is used as the new one.
MC:NII MAN:ARRAY 36

..
Special Vectur Primitives 108 Nil. Manual
The remaining options wi11 not be detailed at this time. adjust-array currently only
works on one-dimensional arrays. so although not generally useful yet. it has enough to
keep vector-push-extend happy.
12.6 Special Vector Primitives
These functions arc around in NIL for historical reasons. They should general1y not be used
in new code. for reasons which will become clear from reading the descriptions. They arc
documented because they arc used aU over the place in Nil. itself still. and vref in particular is
generated internal hy the compiler from the usc of aref.
vref }'('('lOr index
'111is is absolu(('(J' idflllical to aref when aref is given a vector and a single index. aret is
tJle preferred function to usc in code~ the NIL compiler compiles aref· of it single index as
a call to this internal vector-referencing subroutine.
Because this is the same as aref on a one-dimensional array. It IS Ultcresting to note tJlat
(for a vector with a fill pointer) vref does not usc the vector-length to check if the index
is in range.
vector-l ength vector
For historical reasons, this is the same as length but only accepts a vector as an
argument. If the vcctor has a fin pointer. this is not the same as (array-dimension
l'ector 0). which is the quantity used by vref for boundscheckjng.
12.7 Simple Vectors
Vectors of elcment-type t which are not adjustable and have no fill pointer are implemented
as the primitive data type simple-vector. (This was called simple-general-vector in the
'previous NIL release. Do 1101 misinterpret the name. simple-vector to mean one encompassing
vectors of other clement types.) This type is extensively used in NIL as a building block for more
complicated datastructurcs in NIL. including less· simple arrays. There arc special routines for
creating and manipulating them, which are coded cfficiently by the NIL compiler.
Vectors of this type may be checked for with typep, of course.
lIlake-vector size &key initial-contellts initial-element
Makes a vector of element-type t. size long. Because no complicated array options can be
specified, this will always be a simple vector.
This may be caned make-simple-vector in the future, but the name make-vector will
be preserved indefinitely.
MC:NII.MAN:ARRA Y 36

pa
NIL Manual 109
Bit Arrays
vector &rcst elemellls
This makes a simple vector whose clements are initialized to elements. That is.
(vector 123) => #(123)
svref simple-vee/or index
References a simple vector. This routine, is entirely open-coded by the compiler, with no
error checking; to retain nmtime type and bounds checking. aref must be used.
svref may be used with setf.
This function used to be called sgvref: th41t name is still around.
simple-vector-length vcelvr
. Returns the length of the simple vector "ector.
, This used to be c,.1Jed simpJe-general-vector-length (yow!): that name is still around.
12.8 Bit Arrays
Arrays which contain only bits. which can be used to represent boolean true and false, are
useful in various applications. There arc several functions which perform boolean operations on
arrays of this clement type.
Bit arrays may be more or iess appropnate ior a panlcuiar apphcatlon than integers used to
represent a sequence of bits. Bit arrays (or bit-vectors) may be side-effected: integers may not.
Integers however may be used to represent infinite sets. because they are vinually extended with
their sign: see also section 10.S. page Sl. Bit arrays, of course, may be multi-dimensional.
bit bit-array &rest subscripts
Just like aref (page 103), but only works on arrays of clement-type bit.
setf may be used with bit.
s b 1 t bit-array &rcst subscripts
This is just like bit, but is only for use on simple bit arrays. This can result in much
more efficient code, especially if the bit-array is one-dimensional.
setf may be used with sbit.
b 1 t - an d bit-array-] bit-array ..] &optional resu/t-bit"orroy
bit-ior bit-array-] bit-array-] &optional result-bit-array
b 1 t - xo r bit-array-] bit-array ..] &optional result-bit-array
b1 t-eqv bit-array-] bit-array-] &optional resu/t-bit-array
bit-nand bit-array-l bit-array-] &optionaJ result-bit-orray
bit-nor bit-array-i bit-arra"v-] &optional result-bit-array
bit-andc1 bil-arrl1y-i bil-array-2 &optional result-bit-array
bit-andeZ bit-array-I bit-array-] &optional result-bit-array
bit-orc1 bit-arruy-i bil-array-l &optional resull-bil-array
bit-orcZ bit-array-l bil-array~] &optional result-bit-array
MC:NII.MAN:ARRA Y 36
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Hit Arrays 110
These cnmch together bit-array-/ and bi/-arm)'" 2. pcrfonning the appropriate bitwise
logical operation. bi/-urray-} and bit-array"} must have the same rank and dimensions. If
result-bit-array is nil or not specified. then the . result is a freshly created bit array of the
same rank and dimensions. If it is t. then the resuJlc; are stored in bit-orrar I.
Otherwise. it must be a bit array of the same rank and dimensions as the other two, and
the results are stored intO it
b 1 t - no t hi/-array &optionaJ r{'sult-hit-aml)'
Perfonns a bitwise logic~l1 negation on the contents of bit-array. If rrsull-bil-arroyis nil or
nOl specified. then the result is returned as a freshly created bit array of the same rank
and dimensions as bit-array. If rrsu"-bil-a,.rt~l' is t. then hi/-array is side-effected with the
n~~lIlts. Otherwise. ,.csul,-bihlrmy should be the a hit array of the same ranK ~md
dimensions as bit-arr(l),. undwiU hale the results stored into it.
12.8.1 Simple Bit Vectors
In '". a one-dimensiona1 hit array which is 'not adjus~lblc. nOl dispJaccd~ and has no fin
pointcr. hi represented as the primithe t~ pesimple-bit-vector. which is reprcsented more
efficiently than a more general bit array_ Simple bit vecturs are used as building blocks fur more
complicated stmctures which contain binary data. such as the more complicated bit arrays. and
even arrays of clement-type double-float. There are primitives for accessing variable length fields
from them as (possibly sign-extended) fixnums. (but lIo/general integers. yet). and primitives for
treating them il~ jf th~y w~r~ ~('qllen("~ of f'ight·hjrhyt~
Once upon a time the name for this type was bits. This name still lingers in places. but is :
heing replaced by simple-bit-vector.
maKe-b1t-v8ctor size &key illitial-element initial-contents
. Creatcs a simple-bit-vector size long. If neither initia/-element nor initia/-colltents are
specified, the contents of the created bit-vector are undefined. 'The current implementation
of l'IL storage allocation requires that all allocated. datastructure be initialized, so in fact
the bit-vector will always be initialized to zeros. but this could change in the future.
If illitial-elemelll is specified, it must be either 0 or 1. and the elements of the bit vector
are initialized tothaL
If initial-contents is specified. then it should be a bit vector, and the created bit vector is
initialized to the contents of illilia/-colltell/S. If initial-colltellls is longer than size. the
extra elements arc ignored: jf it is shaner, then the contents of the remaining elcmentsof
the created bit vector arc undefined (just as they arc if neither :initial"'element nor
:initia1-contents are specified). It is an error to specify both illilial-elemtIl1I and initialcoiuenls.
s1mple-b1t-vector .. length simple-hit-vPClor
Returns the length of simp/l""bit-ver;lor.
MC:NII.MA'N:ARRAY 36
23-DEC-83
. ~ ..... ~ ~"
~ .... ". '" .. ~ "'~ " ~ ,. r

•
Nil. Manual 111 Bit Arrays
n 1 bb 1 e simple-bit-vector skip take
Retunls the sequence of bits take long from simple-bit-vector. starting at skip. as a
fixnum. take may range from zero to the number of bit~ representable in a fixnum (30)~
however. if the last. the result will include the sign bit so may be unacceptable for
certain applications. The result is zero-extended.
setf may be used with nibble to replace the field.
n1bble-2c simplc-bit-veClOr skip lake
l.ike nibble. hut the result is sign-extended. 'lbat is •. the result is interpreted as a signed
hinary value from the referenced field.
setf may he used with nibble-2c to replace the field.
get-a-byte simple-bit-vector byte-index
Interprets simple-hit-vector as a sequence of type (unsigned -byte 8). and returns the byteindex
th byte.
setf may he used with get-a-byte.
get - a - byte-2c simple-bit-vector byte-index
Interprets simple-bit-vector as a sequence of type (signed-byte 8). and returns the b)'/eindexth
byte.
setf may be used with get-a-byte-2c.
\1C:NlI.MAN:ARRA Y 36

Strings 112 Nil. Manual
. ]3. Strings
Strings arc vcctors of characters which satisfy the prcdicate string-char-p(page 19).
Although thc gcncric sequence and· array primitives operate on strings, there are two reasons for
having additional functions for strings. For Olle. it is convenient for atomic symbols to be used in
pJace of strjngs~ symbols are not coerced to strings by sequence functions. but they are for most
of the string functions. Additiona1Jy. many of the string functions which compare characters do so
independcnt of the character case: the sequence functions are generally based on thceql predicate
(page 20). so are case dependent.
FH'nlUaJly. the string functions will he generalized to handle arguments which are general
c.:h~tfa

.' ~;,
NIL Manual 113 String Comparison
13.2 String Comparison
When routines deal with boundaries within strings. there are two different conventions
applied. Many functions take range arguments as the lower inclusive bound and the upper
exclusive bound (generally named start and end). These arguments conveniently default to 0 .and
the length of the string (typically). As a general rule. an upper exclusive bound may be explicitly
specified as nil producing behavior as if it were mit specified; this is often necessary in order for
following optional arguments to be spccified.
The other commonty used substring convention is for a starting index and a count (generally
named start and ('OUllt) to be specified. (This convention is used primarily hy subprimithes. and
old 'II functions. not (,0\1\10' LISP functions.) The suhstring in qucstion is that starling at the
index. and proceeding for count characters. Hadng a specified count fun off the string is an
error, and an explicit specification of a count of nil is not allowed. Just about all of the routines
which s,til1 follow this subsequence convention are low-level 1'11. functions. in which the count is a
required argument. so the question of how it defaults if not specified should not arise any more.
Routincs using this convention sometimes n;lme these arguments skip and take rather than start
and COUllt.
string-equal string! siring] &key (starl! 0) (sttlrt20) end! end2
This returns t if the subsequence of sIring! from startl (inclusive) to end! (exclusive) is
equal (using case-independent character comparison. ala char-equal (page 95» to the
subsequence of string] from starf2 (inclusive) to end] (exclusive). The subsequences are
St!~r~!!tccd to he uncqu:1! if t.."c ~!.!b$cqucncc lengths differ.
As a special upwards-compatibility hack,
arguments instead of keyword arguments.
string-equal will accept optional position
string-nat-equal stringl string2 &key (startIO) (start20) end/ end2
The opposite of string-equal. Similarly. the subsequences are guaranteed unequal if their
lengths differ.
str1 ng-lessp stringl string2 &key (startl 0) (start20) end! endl
str1ng-not-lessp string 1 string2 &key (starIIO) (slarI20) end! end2
str1 ng-greaterp string! string2 &key (startl 0) (start] 0) endl end2
str1ng-not-greaterp string 1 string2 &kcy (slartl 0) (slart20) endl end2
Each of these returns t if the specified subsequences satisfy the specified ordering
predicate. Basically. the comparison is determined by the first character in the
subsequences which differs (see char-Iessp ctc.. page 95). unless the subsequences are
equa~ in which case a shorter subsequence is t'less than".
As a special upwards-compatibility hack, string-Iessp (but not the other functions) will
accept its arguments positionally rather than by-keyword.
string- string 1 strillg} &kcy (slarIIO) (slort20) end! end}
string/- .~tringl string} &key (startlO) (start) 0) endl end]
str 1 ng< string I string} &kcy (start 10) (slart20) elldl end2
string- slringi slring2 &key (startIO) (starI20) endl end2
MC:NILMAN:STRING 54
23-DEC-83
~ .. . ... -

Extracting Characters from Strings 114 NH. Manual
str i ng> string! string] &key (slartl 0) (sta,,20) elldl elld2
These functions are similar to those above, but do a case dependent character comparison;
that is, they compare the characters like char:: etc. (page 95), rather than char-equal.
]3.3 Extracting Characters from Strings
char Siring index
Returns the indexth character (zero-origined) of the string sIring. as a character object.
sIring must be a string.
Because sIring must hea string. the result uf char will always Stllisfy string-char-p (page
19), with all that that implies.
schar simple-string index
This is like char except that the string must be a simple string. This routine can be
efliciently coded by the NIL compiler.
Like char. schar may be used with setf to store into the string.
13.4 String Creation
make-string length &key :initial-efement
Makes a string irl1gln iong. Since no compiicated array options may· be specI"ed. thIS wiJI
always be a simple-string. initial-elrment must be a character which satisfies stringchar-p;
if it is specified. the returned string contains that charactcrin every element
If initial-element is 110t supplied. the contents of the returned string is undefined by
CO\1MON USP. NIL. which abhors uninitialized memory. will initialize it to zeros (which
happen to be, but may not always be, the character # \Null). If NIL were to be
transported to another operating system with different virtual memory facilities, then this
could change incompatibly.
string-length Siring
Returns the length of the string sIring. string must be a string; it is not coerced.
For COMMON USP, this function is superceded by the generic length function (page 49).
There shou1d be no noticeable efficiency difference between length and string -length. Of
course, string-length will complain if its argument is nota string, whereas length wilt
accept any sequence, including nit
str1ng-upcase Slrillg &.key (slartO) end
stri ng-downcase SIring &1cey (start 0) end
Returns a copy of SIring with all characters converted as by char-upcase (or chardowncase).
If start and/or end arc supplied. then only the specified subsequence of the
result is affected: the result always is the &1melength as SIring. That is. string-upcase
could have been defined as
MC:NfLMAN;STRJNG 54
2.1-I)EC-83

· - ~"''''"
-..w.t"""'_.....,..._______
------~--------------'~-.--~---,----------------
NIL Manual 115 More String Functions
(defun string-upcase (string &key (start 0) end)
{nstring-upcase (copy-seq string) :start start :end end»
If no characters of the string are affected by the conversion. one may not depend on
whether the result is string itself or a copy of it; to guarantee a copy, use copy-seq and
nstring-upcase. as in the above example.
nstring-upcase siring &key (stanO) end
nstri ng- downcase siring &key (slarlO) end
These rOlltines destructively con\'crt all of the characters in the specified suhsequcnce of
slrill~ to upper- or lower-case. siring is returncd.
string-trim character-bag string
S tr 1 ng -1 eft -tr 1m character-bag string
str i n9 - ri ght - tr 1 m character-bag string
Thesc routines rcturn a substring of siring resulting from trimming the characters in thc
"This is a test. "
13.5 l\lore String Functions
The functions in this section are not provided by COMMON USP, but are typically inherited
from LISP MACHI:\E LISP. and are heavily used in NIL. That is also why they havc not yet been
convcrted to takc kcyworded argumcnts (although some of them may be in the future).
str1 ng-append &rcst strings
Returns a string which is the concatenation of all the strings. The arguments are coerced
to strings using string; in this it differs from the generic sequence function concatenate
(page 50), which will not accept symbols, but will accept sequences (of characters) other
than strings.
substring string start &optional end
Returns the substring of string (coerced to a string using string) from the index start up
to but not including end. which defaults to thc length of string if nil or not specificd. If
the specified subsequence is the entire string. one may not depcnd on whether the
returned result is string itself, or a copy; to guarantee a copy. subseq (pagc 50) may be
used-howcver. subseq neither restricts its input to strings nor coerces symbols to strings.
string-reverse string
str1ng-nreverse Siring
These are pretty much superceded by reverse (page 52) and nreverse (page 52). Notc
that for string - nreverse. Siring must be a rcal string bccause it is destructively reversed;
string-reverse will accept a symbol and rcturn a string.
MC:NILMAN:STRING 54
23-DEC-83

Implementation Suhprimitivcs 116
N I J. M~Ulual
s t r 1 n 9 - sa arc h -c h a r char sIring &optionaJ (from 0) 10
string-reverse-search-char char string &optional from (tvO)
str1ng-search-not-char char SIring &optional ({ramO) 10
str1ng-revarsa"'s8arch-not-char char slrillg &optional from (toO)
str1 ng-saarch-set char-set string &optional (from 0) 10
str1ng-raverse-saarch-set char-set string &optional from (toO)
string-search-not-set cha,..set string &optional (fromO) 10
str1ng-reverse-saarch-not-set('ha,..sl'l string &optional from (100)
char-srt is coerced into a sequence of characters: it should be a string. or a list or vector
of ohjects acceptable to character (page 96).
str i ng-search key SIring &optional (from 0) to
str 1 ng - reverse - search key SIring &optional from (/00)
Ll6 Implementation Subprimitives
Th~ roulines descrihed in thb section are very fllst routines pnmltlve'S which arc orienled
toward~ being open-compiled. As such. the}' perfonn very few niceties Jikeargumelll det~lUlting.
The versions available in the interpreter probably will do some error checking~ but don't count on
it. These are the Sluff' of which higher-level routines are made. '111ose which lake string
arguments only accept simple strings.
%s tr1 ng- cons length jill-character
Creates a primitive string length long. filled with the character jill-character, Calls to
make-string will compile into calls to this. if possible. so one should not go out of the
way to use this,
%str1 ng-posqcharacter string index count
This searches through string starting at index and proceeding for count characters for the
character character. If it is found. then the index at which it occurs is returned;
otherwise nil is returned. This primitive only looks at the code attribute of character.
ignoring the rest
%str1ng-eqv string! string] index! index} count
Rcturnst if the substrings of string I and string2 defined by index!, index2. and count
arc string = -that is, the same, with case being significant.
%str1ng-replace destination source deslillation-index source-index counl
This transfers COUllt characters from the simple-string source to the simple string
des/ination, starting at the given indices.
%str1 ng-trans 1 ate destillation source trallslalion-table destination-index source-index counl .
This is a slightly hairier version of %string-replace, Instead of the characters being
transferred literally. the code of each character taken· from the string source is used as an
index in the string trallslation-table to obtain the code to store instead. For example,
string - upcase could be defined
MC:NII.MAN:STRING 54
23-DEC-83

Nil. Manual 117 Imp1cmcnt~lion Subprimitives
(defun string-upcase (string
&aux (len (string-length string»))
(%string-translate
(make-string len) string *:character-upcase-table
o 0 len»
where *:character-upcase-table has as its value a string char-code-limit long whose
ith character is the uppercase version of the character with code i. Note that this
definition of string-upcase is not correct if the input sIring is not a simple-string. and
note also how this relates to how string-char-p is defined.
String hashing in ~IL
is ultimately performed by the eRe instruction.
%str1ng-hash sIring erc-tab/e slar! ('(JUllI
This performs a hash comput..1tion on the substring of SIring starting at character starT and
proceeding for cowll characters. ere-table must be a simple bit vector 512 bit.; (16 \'AX
]ongwords) long: it should contain the hash polynomial for usc by the eRC instruction.
Several hash polynomial tables arc pf(l\'ided (they arc listed below). The hash
computation is initially -1: tllt.~ result is returned as a signed 'II fixl1um-that is. a 32-bit
word with the lop two bits shifted otl'. Consult the VAX architecllIre manual. or some
other DEC documentation. to set up other hash polynomials.
For this to be properly useful for incrementally generating CRe computations. this
primitive will have to be changed to somehow input and output full 32-bit quantities;
*:autod1n-11-hash-polynom1al
*:cc1tt-hash-polynom1al
*:crc-16-hash-polynomial
This is the one NIL uses for doing intern and sxhash of strings.
J;ariablc
Variable
Variable
MC:NILMAN:STRING 54
23-DEC-83

-. • • • _': - " .~.
• - - - '.' - • ," .:: • • .-' -- .'. - • •
Hashing 118 Nil. Mamwl
14. Hashing
Nil. supports a COMMON JJSP compatible hash-table facility. This will eventually include the
ability to have a hash-table from which associations can be garbagc-conected.
14.1 Hash Tables
The following routines are COMMON I.ISP compatible:
make-hash-table &key :test :rehash-threshold :rehash-size :size
Cr{,~ltcs .. hash tahle. The tcs/ m,l}, be one of # 'eq.' # 'eql. or # 'equal. NIL
,uJditionaHy provides some others it is able to perfonnsignific,mt optimizations on as
primith'e (see hclow). Note t11m fi.lr 1'11. () usc some predicate it must know how to
compute a hash code compatible with that predicate'snotion of equality: thUS. not just
any predicate is acceptable.
get hash kcy haslf"lable &optional dejault
This returns two valucs. If there is an entry for key in hash-lab/e. then this returns as its
v41lues the value associated with key. and t. Otherwise. it returns default. and nit
gethash may be used with setf to add an entry to (or replace an entry in) a· hash table.
remhash key hash-table
Removes the cntry associated with key from hash-Iable.
cl rhash hash-fable
Removes al1 entries from hash-lable.
hash - tab 1 e - count hash-table
Returns the number of entries in hash-lable.
14.1.1 Additional Hash-Table Predicates
NIL additionally offers the following predicates for hash-tables:
string -equal
string= '
associating hashing routines with predicates, making this list extensible?
MC:NII.MAN;HASH20
23-DEC-83
".;,. ..... ~ , - ~. I , ~
. ~ -. .~: ~ - ~ ~ -, : : ~
- .... I " • • _ ..
. .". v. . " '. f' ~"
•
•

NIL Manual 119 Hash Functions
14.2 I lash Functions
A hash function for equality predicate (p xl. x2) is a function which returns the same value
for all x which are equivalent according to p. "The standard LISP hashing function is sxhash.
which is defined according to the equal predicate. sxhash is inherited from MACUSP. and is
defined by CO~1MON LISP and LISP MACHINE LISP;
Other hash functions are defined by ~IL. for use with other equality predicates. Usually they
are not needed. because tJley are impJied in me use of a hash table utilizing a particular equality
predicate. Ry convention. all 'II. hashing functions return a non-negative fixnum: it is a fixnum
for ease of computation. and non-negative to make modulus operations more trivial.
sxhas h ()~;ecl
This is tJle general J .ISP hashing function. hased on the predicate equal (page 20). hit
.returns a non-negative integer: in NIL, this will always be a fixnum. Two objects which
are equal should always sxhash to me same tJling. If tJ1is is not true. then any hash
~1hles which use sxhash and equal will break. Note that hecause !'II will have a
relocating garbage collector, the hash of In object should never be a function of the
address of anything.
str i ng-equa l-hash string
This function returns a non-negative fixnulTI such tJlat for all strings which are stringequal.
tJleir hashes computed by this function will be equal.
str1ng a -hash Siring
Similar; defined by the predicate string = (page 113).
sys: sxhash-comb1 ne {hash} +
This macro might be useful to writers of :sxhash methods or special hashing functions. It
is a canonical way to combine a fixed number of hash codes. For example, the sxhash
of a cons docs
(sys:sxhash-combine (sxhash (car x)} (sxhash (cdr x)})
The hashes are rotated some fixed amount detennined by the number of arguments, and
crunched together in some canonical fashion. (There may be a limitation on the number
of arguments which are handled, but this will work for some moderate number of
arguments.)
14.3 Symbol Tables
Although one can use packages to implement symbol tables. and this has been recommended
in the past. it is now better to use a hash table based on the appropriate predicate. and storing
'an appropriate object as the value. For example, if one had been using a package as a symbol
table and then using the symbol after interning it. a hash table could be used using string-equal
or string = as the predicate (as appropriate) and putting a symbol in as the valuc. Dcpending on
what the symbol is used for. it may be better to use a defstruct-created object instead: attributes
can be accessed fasler off of this than as properties on the pliSl of a symbol. Secondarily. there is
a moderate space inefficiency to gener3ting lots of value ceBs in Nil" so instead of generating
symbols and using their value cells to store things is also better to usc a specialized structure.
~1C:NII.MAN:H"SH 20
2J-DFC-83

Symbol Tables 120 Nil. M,lnual
When the ~n. package system is redone. the intcrna1 portion of that which docs simple
symbol-table hacking will be made· available fi)r applications where that is truly nceded.
~1C;NJL~1.\~:HASH 20

NIL Manu~l 121 Packages
15. Packages
Skctchy. This is all going to brcak. either as a result of COMMON LISP or complete
rcimplcmcntation and redesign or both.
understanding of simple obarrays/ob/isls and interning is assumed below
The basic idca of packages is that if an programs in a large messy environment like NIL use
the same name-sp

Packages 122 NIL Manual
A little thought «thOllt the use of the sys and global p~lckages in the ahove description will
show that they should nO( be ordin

NIL Manual 123 Modules
15.1 Modules
CO!\1!\10~ LISP defines a fairly simple way in . which one may name modules. declare that they
have been loaded, and cause them to be loaded if they have not been. While t11is is intended to
be used as a part of the COMMON LISP package system. it is fairly independent and can be used
without it. Here it is.
In this sense. a module (not to be confused with the NIL data type module which will be
renamed someday) is simply an independent subsystem which is treated as a unit. A module can
come from one or more files: the' number is irrelevant other than to the loading process.
CO\1\10,\ liSP modules arc referenced by name: functions which take a module name may he
given either a string or a symhol. In the module name. case mailers. so. f()r instance. "LSS" is
not the same module name as "Isb".
• modul as.
Variable
This variable has as its value a list of the names of all the modules which have been
provided (see be1

Modules 124
NII~ Manual
note-modu18-pathname module-1lome po/hllam!'
This declares that in order to provide lIlodule-llame. pal/mallle must be loaded. palhllome
may also be a list of pathnames.
Eventually. higher-level ways of defining packages, systems. and modules wiU be defined.
and use of note-modufe-pathname will be phased out.
The only modules known about in advance by the NIL system right now LS8 and SIMP. Of
course. as of this writing. the fc1cilitics documented in this. section haven °t even been installed yet.
so there will probably be severa) tnoreshonly .
...
!\1C:NII.\1AN:PACKAG 17
23-DEC-S3

NIL Manual 125 Defstruct
16. Defstruct
) 6.1 Introduction
This chapter is a modification of the description of defstruct appearing in the MacIisp
Extensions Manual [3]. There are three sorts of ~hangcs:
(I) Deletion of topics not applic~bJe) to NIL;
(2) Deletion of things which do not yet work in NIL;
(3) Modifications of the defaults. as the NIL defstruct is intended to be upwards-compatible
with the CO\1\HY\ IISP defstruct.
For these reasons. some of Ule wording m~'y seem a bit strange. in that the original document is
concerned with helping users write code compatible in differing l.isp implementations. defstruct
is part of the ('0\1\10;\ I.ISJ> st4tndard (but not all the parts of it). and the documentation on it
will be fixed in the future. Any inaccuracies in this modification of it are purely the fault of
GSB.
The keywords which are used in defstruct arc all interned in the keyword package. just like
Olher keY\H)rds in :\11.. For compatibility with \tACI.ISP programs. howe":-f. defstruct \\-'ill accept
UlOse 1101 in me keyword package. Convcrsely. the MAC'I.ISP def.~truct will check f(lr symbols
which have a leading "." in their names. In !'IL. one should use the colons for stylistic
consistcncy.
16.2 A Simple Example
defstruct
defstruct i~ a macro defining macro. The best way to explain how it works is to show a
sample call to defstruct. and thcn to show what macros are defincd and what each of
them does.
Sample call to defstruct:
(defstruct (elephant (:type :list»
color
(size 17.)
(name (gensym»)
This fonn expands into a whole rat's nest of stuff, but the effect is to define five macros:
elephant-color, elephant-size. elephant-name. make-elephant and alter-elephant. Note that
none of these symbols appeared in the original form, they were created by defstruct. The
definitions of color. size and name are easy. they expand as follows:
(elephant-color x) ==> (car x)
(elephant-size x) ==> (cadr x)
(elephant-name x) ==> (caddr x)
You can see that defstruct has decided to implement an elephant as a list of uucc things~ its
color, its size and its name. The expansion of make-elephant is somewhat harder to explain,
let's look at a few cases:
MC:NILMAN;DEFSTR 91
23-DEC-83

57 - -.- v 'to ,
I
Syntax of de fstruct 126
Nil. Milfiual
(make-elephant) ==> (list nil 17. (gensym»
(make-elephant :color 'pink) ==> (list 'pink. 17. (gensym»
(make-elephant :name 'fred :size 100)
==> (list nil 100 'fred)
As you can sec, make-elephant takes a "sctq-stylc" list of pan names and forms, and
expands into a call to list that constructs such an elephant. . Note that the unspecified pans get
defaulted to pieces of code specified in the original caU to defstruct. Note also that the order of
the sctq·style arguments is ignored in constructing the call to list. (In the example. 100 is
evaluated before 'fred even though 'fred came first in the make-elephant form.) Care should
thus he taken in usjng code with side effects within the scope of a make-e1ephant. (This
particular hehaviour will be "fixed" by (,O\1MO~ LISP. hut has not yet been worked into \11.)
Finally, wke note of the fact thai the (gensym) is evaluated el'C'IJ' lime a new elephmltis creilled
(unless you override it).
The explanation of what alter-elephant docs is delayed until section 16.4.3. page 129~
So now you know how to construct a new elephant and how to examine the parts of an
elcph.mt. but how do you ch.mgc the pare; of an already existing elephant? The answer is to use
the setf m,tcro (section 5.9 t page 38).
_(s e t f (e 1 e p han t - n arne x) 'b i 11 ) = = > ( set f (c add r x) , bill )
which is what you want.
A nt1 th!lt ~5 jU5t about an t"~rc -is t{' defstruct: you now know enough to use it in your cede.
but if you want to know about all its interesting features, then read on.
16.3 Syntax of derstruct
The general fonn of a defstruct fennis:
(defstruct (name opt;o"..1 0pl;0n-2 ••• option-n)
slot-description-I
slot-description-2
s/ol-descriplion-m)
name must be a symbol. it is used- in constructing names (such as_ "make-elephant") and it is
given a defstruct-description property of a structure that describes the structure completely.
Each oplion-i is either the atomic name of an option. or a Ust of the form (option-name arg •
res/). Some options have defaults for arg; some will complain if they are present without ail
argument: some options complain jf they are present with -an argument. The intcrpretationof rest
is up to the option in question. but usually it is expected to be nit
Each SIOI-dcscriplioll-j is either the atomic name of a slot in the structure. or a list of the
form (slot-Ilome illit-C'ode). or a list of byte field specifications. illil-code is used by constructor
macros (such as make-etephant) to initi~1ize slots not specified in the call to the constructor. If
the illil .. code is not specified. then the slot is initialized to whatever is most convenient. (In the
elephant example, since the structure was a list. nil was used. If _ the structure had been a
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fixnurn array. such slots would be fined with zeros.)
A bytc field specification looks like: (field-name bytespec) or (field-name bylespec illit-code).
Notc that since a byte field specification is always a list. a list of byte field specifications can
never be confused with the other cases of a slot description. The byte field feature of defstruct
may be undergoing change in !'I:II. due to the incompatible change of bytespec format (see section
10.9. page 84). so is discouraged for the present·
16.4 Options to defstruct
The following sections document each of the options defstruct understands in detail.
On the Lisp Machine and in ~II..
package.
an these defstruct options are interned on the keyword
16.4.1 :type
The :type option specifics what kind of lisp object defstruct is going to use to implement
your structure. and how that implementation is going to be carried out. The :type option is
illegal without an argument. If the :type option is not specified. then defstruct will choose an
appropriate default: in I'lL. defstruct will implement the structure as a vector-like object. which
will be defined as a type whose name is the name given to defstruct. One can then check for
objects ot thiS type with typep. (This dittcrs from the way defstruct currently operates in
\1:\('I.ISI> and I.IS}> M:\C'IIINF LISP.) It is possible for the user to teach defstruct new ways to
implement structures, the interested reader is referred to section 16.6, page 138, for more
information. Many useful types have already been defined for the user. A table of these "built
in" types follows.
:Iist
:named-list
:tree
:list.
Uses a list This is the default in MULTICS MACUSP.
Like :list, except the car of each instance of this structure will be the name
symbol of the structure. This is the only "named" structure type defined on
Multics and is the default named type there. (See the :named option documented
in section 16.4.4, page 131.)
Creates a binary tree out of conses with the slots as leaves. The theory is to
reduce car-cdring to a minimum. The :include option (section 16.4.9, page 133)
does not work with structures of this type.
Similar to :list. but the 1ast slot in the structure wi11 be placed in the cdr of the
final cons of the list. Somc people caB ohjects of this type ttdotted lists". 111C
:include option (section 16.4.9. page 133) does not work with structures of this
type.
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: array
:sfa
:vector
Uses an array object (not a symbol with an array property). This is the default on
Lisp Machines. Eventually. many of the same hairy array options which defstruct
supports on the Lisp Machine will be supported in NIL; at this time. however.
NIL users are advised to just usc the default, or perhaps :vector.
Uses an SFA. The constructor macros for this type accept the keywords :sfafunction
and:sfa-name. Their arguments (evaluated. of course) are used.
respectivcly. as the function and the printed represenwtion of the SFA. See also
the :sfa-function (~cli(}n 16.4.12. page 134) and :sfa-name (section 16.4J3. page
135) options. (SFAs ,tre clvailahle in ~n. for compatibility with PDP-IO \1 ACIISI).
They should not nonnally be used. and HfC not documented in the 'II m~lJlual.)
Uses an vector. This will be a simple-vector.
:nl\med - vector
I -ike \ ector. ex,:cpt clement number 0 illways contains the n(lme symbol of the
structure. Note thUl this is 110/ Ule default lIdmcd type in Nil .• :extend is.
:extend
'Ibis is the default named type in ~IL. Nonnally you don't need· to know that it
h~~ thi" w~ird T1;l1T'!('. h~m,se thi5 has bc~n the d~f:m!! dcfS!!"uct typ~ if :namse is
specified for a \\'hile. and it is now the def4Juh type period. See also the :classsymbol
option (section 16.4.11, page 134).
) 6.4.2:constructor
The :constructor option specifics. the name to be given to the constructor macro. Without an
argumen~ or if the . option is not present. the name defaults to the concatenation of "make..·' with
the name of the structure, If the option is given with an argument of nil. then no constructor is
defined. Otherwise the argument is the name of the constructor to define. NonnaUy the syntaX
of the constructor defstruct· defines is:
( COIlSlTUClo~nQme
keyword-J code-J
keyword-2 codeo2
keyword-n code-n)
Each keyword- i must be the name of a slot in the structure. or one of the special keywords
allowed for the particular type of structure being constructed. . All of these keywords are symbols
interned in the keyword package. although for upwards-compatibility (this is new behaviour) that
is not required. For each keyword that is the name of a slot. the constructor expands into code
to make an instance of the structure using ('odr-i to initialize slot keyword-i. Unspecified slots
default to the forms given in the original defstruct fonn. Of, if none was given there. to some
convenient value such as nil or O.
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For keywords that are not names of slots. the use of the corresponding code varies. Usually
it controls some aspect of the insUlnce being constructed that is not otherwise constrained. The
only one of these which is used in NIL is the :sfa-function option (section 16.4.12. page 134).
If the :constructor optior is given as (:eonstruetor Ilame arglis!). then instead of making a
keyword driven constructor. defstruet defines a ttfunction style" constructor. The arglist is used
to describe what the arguments to the constructor will be. In the simplest case something like
(:constructor make-foo (a b e» defines make-foo to be a three argument constructor macro
whose arguments are lIsed to initialize the SIOLIi named a. band c.
In addition. the keywords &optional. &rest and &aux are recognized in the argument list.
They work in the way you might expect. but there are a few fine points worthy of explan

W ·lrV"·
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130
made to be the vallie of slot s!o/-llome-; of that structurc. lbe slots are an altcrcdin paralle1
alief all code has been evaluated. (Thus you can usc an alterant macro to exchange the contents
to two slots.) As for the kcywordcd constructor macro. the s!ot-Ilame-i should be symbols interned
in the keyword package. although (again) that is not required.
Example:
(defstruct (lisp~hacker
(favorite~macro-package
(unhappy? t)
(number-of-friends 0»
(:type :11st)
:conc-name
:defau1t-pointer
:a1terant)
nil)
(setq lisp-hacker (make-lisp-hacker»
Now we can perfonn a transfonnation:
(alter-lisp-hacker lisp-hacker
favorite-macr0-package 'defstruct
number-of-fribnds 23.
unhappy? nil)
==> «lambda (G0009)
« lambda (GOOI1 GOOIO)
(setf (car G0009) 'defstruct)
lsett (caaar uOOOY) uOOll)
(setf (cadr G0009) GOOIO»
23.
nil»
lisp-hacker)
Although it appears from this example that your fonns will be evaluated in the order in
which you wrote them~ this is not currently guaranteed.
Alterant macros are particularly good at simultaneously modifying . several byte fields that are
allocated from the same word. They produce better code than you can by simply writing
consecutive setfs. They also produce bener code when modifying several slots of a structure that
uses the :but-first option (section 16.4.17, page 135).
For defstruct types whose accessors take more than one argument. all of those arguments
must be supplied to the alterant macro in place of just the usual one. (Sec section 16.6.3.2, page
140 for how accessors with more than one argument can come to be, there are no built-in
defstruct types with this propcny.)
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NIL Manual 131 Option!'. to dcfstruct
16.4.4 :named
This option tells defstruct that you desire your structure to be a "named structure". In PDP-
10 \1ACl.ISP this means you want your structure implemented with a :named-hunk, :named-list
or :named-vector. On a Lisp Machine this indicates that you desire either a :named-array or a
:named-array-Ieader or a :named-list. On Multics this indicates that you desire a :named-list.
In ~IL this indicates that you desire a :extend. a :named-vector or a :named-list. defstruct
bases its decision as to what named type to use on whatever value you did or didn't give to the
:type option: in NIL. the default named type is :extend. and :named is the default-the
significance of this was explained in section 16.4.1. page 127. It is an error to usc this option
with an argument.
16.4.5 :predicate
The :predicate option causes defstruct to generate a predicate to recognize instances of the
stmcllIre. Naturally it nnh' works for some ~efstruct types. Currently it works for all the named
types as we11 as the types :sfa {PDP-tO \1ACUSf) and :\IL only) and :extend (:\11. only). The
arg.ulllcnt to the :predicate option is the name of the predicate. I f it is present without an
argument, then the name is formed by concatenating "_p" to the end of the name symbol of the
stmcture. If the option is not present then no predicate is generated. Example:
(defstruct (foo :named :predicate)
foo-a
foo-b)
defines a single argument function. foo-p. that is true only of instances of tJlis stmcture.
16.4.6 :print
The :print option al10ws the user to control the printed representation of his structure in an
implementation independent way:
(defstruct (pair :named
pair-first
pair-second)
(:print "{-S . -S}"
(pair-first pair)
(pair-second pair»)
The arguments to the :print option are used as if they were arguments to the format function
(page 187). except that the first argument (the stream) is omitted. They are evaluated in an
environment where the name symbol of the structure (pair in this case) is bound to the instance
of the structure to be printed.
This option presently only works on Lisp Machines and in NIL. using the defstruct types
:named-array and :extend respectively. We hope to make it work in rDP-10 \1ACl.lSP for the
:named-hunk type soon. In MULTICS MACLlSP. this option is ignored. Notice that if you just
specify the :named option without giving an explicit :type option. each defstruct implementation
will default to a named type that can control printing if at all possible.
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Optiuns to defstruct 132 Nil. M.tnual
16.4.7 :default-pointer
Normally the accessors are defined to be macros of exactly one argument. (They check!) But
if the :default-pointer option -is present then they will accept zero or one argument. When used
with one argument. they behave as before. but given no. arguments. they expand as if they had
been called on the argument to the :default .;.pointer option. An example is probabJy caned for:
(defstruct (room (:type :tree)
(:default-pointer •• current~room •• )}
(room-name 'y2)
(room-contents-list nil»
Now the accessors expand as follows:
(room-name x)
(room-name)
==>
==>
(car x)
(car •• current-room •• )
If no argu~ent is given to the :default-pointer option. then the name of the stnJcture is
used as the "default pointer". :default- pointer is most often used in this fashion.
16.4.8 :conc"name
Frequently all the accessor macros of a· stnteture will want to have names that begin the same
way: usually with the name of the stnlcture followed by a dash. The :conc-name option Clllows
the user to specify this prefix. Its argument should be a symbol whose print name will be
concatenated onto the front of the slot names when forming the accessor macro names. If the
argument is not given. then the name of the structure fbl10wed by a dash is used. as it is if the
:conc-name option is not prcscnL(This is different than it used to be!) If it is desired that the
slot names. as specified. be used' as the accessor macros. then (:conc-name nil) may be used.
An example illustrates a common use of the :conc-name option along with the :default-pointer
option:
(defstruct (location :default-pointer
:conc-name)
(x 0)
(y 0)
(z 0»
Now if you say
(setq location (make-location x 1 y 34 z 5»
it will be the case that
(location-y)
will return 34. Note wen that the name of the slot ("ytt) and the name of the accessor macro for
that slot ("location y") are different
w
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NIL Manual 133 Options to defstruct
16.4.9 :include
The :include option inserts the definition of its argument at the head of the new structure's
definition. In other words. the first slots of the new structure are equivalent to (Le. have the
same names as. have the same inits as. etc.) the slots of the argument to the :include option.
The argument to the :include option must be the name of a previously defined structure of the
same type as the new one. If no type is specified in the new structure, then it is defaulted to
that of the included one. It is an error for the :include option to be present without an
argument. Note that :include does not work on certain types of structures (e.g. structures of type
:tree or :Iist.). Note also that the :conc-name, :default-pointer. :but-first and :callableaccessors
options only apply to the accessors defined in the current defstruct: no new accessors
arc defined f(.lf the included slots.
An example:
,(defstruct (person (:type :list})
name
age
sex)
(defstruct (spaceman (:include person)
(:conc-name nil)
:defau1t-pointer)
helmet-size
(favGrit~-b~v~rag~ 'tang})
Now we can make a spaceman like this:
(setq spaceman (make-spaceman :name 'buzz
:age 45.
:sex t
:helmet-size 17.5»
To find out interesting things about spacemen:
(helmet-size)
==> (cadddr spaceman)
(person-name spaceman) ==> (car spaceman)
(favorite-beverage x) =:> (car (cddddr x»
As you can see the accessors defined for the person structure have names that start with
"person-" and they only take one argument. The names of the accessors for the last two slots of
the spaceman structure are the same as the slot names, but they allow their argument to be
omitted. The accessors for the first three slots of the spaceman structure are the same as the
accessors for the person structure.
Often. when one structure includes another. the default initial values supplied by the included
structure will be undesirable. These default initial values can be modified at the time of inclusion
by giving the :include option as:
(: include name new-init-] ••. new-fnil-n)
Each Ilcw-fnit-i is either the name of an included slot or of the fonn (included-slot-name new-init).
If it is just a slot name. then in the new structure (the one duing the including) that slot will
have no initial value. If a new initial" value is given. then that code replaces the old initial value
code for that slot in the new structure. The included structure is unmodified.
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Options to defstruct 134 NIL Manual
16 .• 4.10 :copier
This option causes defslruct to generate a single argument function that will copy instances of
this structure. The argument to the :copier. option is the name of the copying function. If this
option is present without all argument. then the name is formed by concatenating "copy-" with
the name of the structure.
Example:
(defstruct (coat-hanger (:type :list) :copier)
current-closet
wire-p)
Gen(.~r'llcs a function ~Ipproximatcly like:
(defun copy-coat-hanger (x)
(list (car x) (cadr x»)
16.4.11 :class .. symbol
For use with tlle :extend defstruct type ~l\·ai1ahle only in :\11 (section Io.'U. page 128). this
option allows the lIser to control hem' the flavor definition is pcrfimlled. '( his option IIIWil be
given a variable name as an argument: the value of that variable is used as the flavor (class)
object of the object which the defstruct-defined constructor will create. defstruct wi11 not define
the flavor.
This option W~)S originally implemented for bootstrapping purposes. so that typed objects in
!':Il. could be created before the flavor system was fully loaded. Pventually it will be fully
outmoded by extensions to the flavor system, which already has the capability of defining accessor
macros for instance variables.
16.4.12 :sfa-function
Available in PDP-IO MACUSP and in NIL. this optionaUows the user to specify the function
that will be used in structures of type :sfa. Its argument should be a piece of code that evaluates
to the desired function. Constructor macros for this type of structure will take :sfa-function as a
keyword whose argument is also the code to evaluate to get the function. overriding any supplied
in the original defstruct form.
If :sfa ,..function is not present anywhere, then the constructor will use the name-symbol of
the· structure as the function.
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16.4.13 :sfa-name
Available only in PDP-IO MACI.ISP and 1'0:11.. this option allows the user to specify the object
that will be used in the printed representation of structures of type :sfa. Its argument should be
a piece of code that evaluates to that object. Constructor macros for this type of structure will
take :sfa-name as a keyword whose argument is also the code to evaluate to get the object to
usc, overriding any supplied in the original defstruct fotm.
If :sfa-name is not present anywhere. then the constructor will use the name-symbol of the
stnlcture as the function.
16.4.14 :sizc-symbol
The :size-symbol option allows a user to specify a symbol v.hose value will be the "size" of
the stnicture. The exact meaning of this varies, but in general this number is the one you would
need to know if you were going to allocate one of these structures yourself. The symbol will
have this vallie both at compi1e time and' at run time. If this option is present without an
argument. then the name of the structure is concatenated with "-size" to produce the symhol.
16.4.15 :size-macro
Similar to :size-symbol. A macro of no arguments is defined that eXPands into the size of
the structure. The name of this macro defaults as with :size-symbol.
16.4.16 :initial-orrset
lbis option allows you to tell defstruct to skip over a certain number of slots before it starts
allocating the slots described in the body. This option requires an argument. which must be a
fixnum, which is the number of slots you want defstruct to skip. To make use of this option
requires that you have some t:'UTliliarity with how defstruct is implementing you structure,
otherwise you will be unable to make use of the slots that defstruct has left unused.
16.4.17 :but-first
This option is best explained by example:
(defstruct (head (:type :list)
nose
mouth
eyes)
(:conc-name nil)
(:default-pointer person)
(:but-first person-head»
So now the accessors expand like this:
(nose x) ==> (car (person-head x»
(nose)
==> (car (person-head person»
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Options to def.~lruct 136 NIL Mmlllill
The theory is that :but-firsfs argument will likely be an accessor from some other stnlcture.
and it is never expected dlal this structure will be found outside of that slot of that other
structure. (In the example I had in mind that thefe was a person structure which had a slot
accessed by person~head.) It is an effor for the :but-first option to be used without an
argument.
16.4.18 :callablc-accessors
This option controls whether the accessors defined by defstruct will work as "functional
ar!!Ullll'1l1S" (as the first argument to mapcar. for example). On the I.isp Machine and in ~II.
m.:ccs~or\ arc GJllahlc hy dcfitUll. but inPI>P-W \iA(,IISP it is cxpenshe to milke this work, so
the~ arc only caHahle if you ask for it. (Currently on Multks the feaLUre doesn't work at all ..•)
The argument to this option is nil to indicate that the feature should he turned off. and t to turn
the feature on .. If the option is present with no argument. then the feature is turned on.
16.4.19 :cl'al-when
Normally the macros defined by defstruct are defined at c\al-time. compile-time 4md at loadtime.
This option allows the user to control this behavior. (:eval-when (evaJ compile»~ for
example. will calise the macros to he defined only when the code is nmning interpreted and
inside the compiler. no trace of defstruct wiJ] be found when running compiled code. (See evalwhen.
page 25.}
Using the :eval-when option is preferahle to wrapping an evaJ-when around a defstruct .
fonn. since nested eval-whens can interact in unexpected ways.
16.4.20 :property
For each structure defined . by defstruct, a propeny list is maintained for the recording of
arbitrary propenies about that structure.
The :property option can be used to give a defstruct an arbitrary propeny.· (:property
properly-name value) gives the defstruct a property-name propeny of value. Neither argument is
evaluated. To access the propeny list. the user will have to look inside the defstruct-description
structure himself, he is referred to section 16.5, page 137. for more information.
16.4.21 A Type Uscd As An Option
In addition to the options listed above, any currently defined type (a legal argument to the
:type option) can be used as a option. This is mostly for compatibility with the old Lisp Machine
defstruct. It allows you to say just type when you should be saying (:type type). Use of this
feature in new code is discouraged. It is an error to give an argument to a type used as an
option in this m,tnner.
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16.4.22 Other Options
Finally, if an option isn't found among those listed above, defstruct checks the property list
of the name of the option to see if it has a non-null :defstruct-option property. If is docs have
such a property. then if the option was of the fonn (optiOlrname value). it is treated just like
(:property option-name value). That is. the defstruct is given an option-name property of value.
If such an option is used without an argument. it is treated just like (:property op/ion-name t).
That is. it is treated as if the argument was t.
'Illis provides a primitive way for the user to define his own options to defstruct. Severa} of
the options listed ahove are actually imp1cmel1lcd using this mechanism.
16.5 The defstruct-description Structure
This section discusses the internal structures used by defstruct that might be useful to
programs that want to interface to defstruct nicely. The infonnation in this section is also
necessary for anyone who is thinking of defining his own structure types (section F.6, page 138).
l.isp Machine and 'II programmers will find that the symbols found only in this section arc all
interned in the "systems-internals" package ("51" for short).
Whenever the user defines a new structure using defstruct. defstruct creates an instance of
the defstruct-description structure. This structure can be found as the defstruct-description
property of the name of the structure: it contains such useful infonnation as the name of the
structure. the number of slots in the stnlcture. etc.
The defstruct-description structure is defined something like this: (This is a bowdlerized
version of the real thing, I have left out a lot of things you don't need to know un1ess you are
actually reading the code.)
(defstruct (defstruct-description
(:default-pointer description)
(:conc-name defstruct-description-»
name
size
property-alist
slot-alist)
The name slot contains the symbol supplied by the user to be the name of his structure.
something like spaceship or phone-book-entry.
The size slot contains the total number of slots in an instance of this kind of structure. This
is not the same number as that obtained from the :size-symbol or :size-macro options to
defstruct. A named structure. for example~ usually uses up an extra location to store the name
of the structure. so the :size-macro option will get a number one larger than that stored in the
defstruct description.
Pille property-alist slot contains an alist with pairs of the fonn (properly-name. properly)
containing properties placed there by the :property option to defstruct or by property names used
as options to defstruct (see section 16.4.20, page 136. and section 16.4.22, page 137).
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The sfot-aiist slot contains an alis( of pairs of the fimn (slot-name. slot-description). A slot·
descripliol1 is an ins~lnce of the defstruct-slot-description structure. The defstruct-slotdescription
structure is defined something like this: (another bowdlerized defstruct)
(defstruct (defstruct-slot-description
(:default-pointer slot-description)
(:conc-name defstruct-slot-description-»
number
ppss
init-code
ref-macro-name)
The number slot contains the number of the location of this slot in an instance of the
structure. l.ocations arc numhered starting with O. and continuing lip to one less than the size of
the structure. The actual location of Ule slot is detennined by the reference c(lnsing code
associated with ule type of the structure. See scction16.6. page 138.
The ppss slot contains the 'byte specifkr cod~ for this slot if this slot is ~ byte field of its
Jocation. If this slot is the entire location. then the ppss slot contains nil.
The init-code slot contains the initialization code supplied for this slot by the lIser in his
defstruct form. If there is no initialization code for this slot then the init-code slot contains the
symbol %%defstruct-empty%%.
Thl' r~f-rn~('r(\-narn~ ~~(\t ('(\ntains th~ sym1)(\! lllat is d('fin('d as an nccessor t.~Jt references
this ,slot.
16.6 Extensions to defstruct
da1struct-det1ne-typ.
The macro defstruct-define-typeean be used to teach defstructabout new types itean
use to implement structures.
16.6.1 A Simple Example
Let us start by examining a sample call to defstruct-define-type. This is how the :list type
of structure might have been· defined:
{defstruct-define-type :11st
(:cons (initialization-list description keyword-options)
:list
(cons -list initialization-list»
(:ref (slot-number description argument)
(list 'nth slot-number argument»)
This is the minimal example. We have provided defstruct with two pieces of code. one for
cnnsing up fonns to constnJct instances of the structure. the other to cons up fonns to reference
various clements of the structure.
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From the example we can see that the constructor c

Extensions to defstruct 140 NIL Manual
The symbol i"ils will be bound to the code that the C(}n~tnlctor conser should use to initialize
the slots of the structure. The exact form of this argument is detcnnincd by the symbol kind.
There arc currently two kinds of initialization. There is the :Iist kind, where illilS is bound to a
list of initializations. in the correct order. with nils in uninitialized slots. And there is the :alist
kind. where illils is bound to an aJist with pairs of the form (s/ot-number . illit-code).
111e symbol description will be bound to the instance of the defstruct-description structure
(section 16.5. page 137) that defstruct maintains for this particular structure. This is so that the
constructor conser can find out such things as the total size of the structure it is supposed to
create.
The symhol k(l'tnmls will be bound (() ,1 alistwith pairs of the foml (kr.l'""orc/. value).
where each kr,l'u:ord was a keyword supplied to the constructor macro that wasn't the name of a
slot. "no rall/r waslhe "code" Ulal followed the keyword. (Sec section 16.6.3.6. page 142. and
section 16.4.2. page 128.)
It is an error not to supply the :cons option to ~efstruct-define-type.
16.6.3.2 :ref
111C :ref option to defstruct-define-type is how the user supplies defstruct with the
nccessary code that it needs to cons up a form that will reference an instance of a stnJcture of
this type.
The :ref option has the syntax:
( : ref (number description arg-J ••. argon)
body)
body is some code that should construct and return a piece of code that will reference an
instance of a structure of this type.
The symbol Ilumber will bc bound to the location of the slot that the is to be referenced.
This is the same number that is found in the number slot of the defstruct-slot-description
structure {section 16.5, page 137}.
The symbol description will be bound to the instance of the defstruct-description structure
that defstruct maintains for this particular structure.
The symbols arg-i are bound to the ·fonns supplied to the accessor as arguments. Nonnally
there should be only onc of these. The /asl argument is the one that will be defaulted by the
:default-pointer option (section 16.4.7. page 132). defstruct will check that the user has supplied
exactly n arguments to the accessor macro before calling the reference con sing code.
It is an error not to supply the :ref option to defstruct-define-type.
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NIL Manual 141 Extensions to defstruct
16.6.3.3 :prcdicate
The :predicate option to defstruct-define-type is how defstruct is told how to produce
predicates for a particular type when the :predicate option to defstruct is used (section 16.4.5.
page 131). Its syntax is:
{ : p red i c ate (description name)
body)
The variable description will be bound to the defstruct-description structure maintained for
the structure we are to generate a predicate for. The variable name is bound to the symhol that
is to he defined as a predicate. b(}{~l' is a piece of code to evaluate to return the defining fonn
f()r the predicate. 1\ lypical lise of this option might look like:
(:predicate (description name)
'(defun ,name (x)
(and (frobbozp x)
(eq (frobbozref x 0)
'.(defstruct-description-name»»)
16.6.3.4 :olcrhcad
The :overhead option to defstruct -define-type is how the user declares to defstruct that the
implementation of this particular type of stnlcture "uses up" some number of slots locations in the
ob.ieer actually constntcted. This option is used hy variolJs "nllmeo" typcl\ of "trtl('tlJr('~ thM ~t(lre
the name of the stnlcture in one location.
The syntax of :overhead is:
(:overhead n)
where II is a fixnum that says how many locations of overhead this type needs.
This number is only used by the :size-macro and :size-symbol options to defstruct. (See
section 16.4.15, page 135, and section 16.4.14, page 135.)
16.6.3.5 :named
The :named option to defstruct-define-type controls the use of the :named option to
defstruct.. With no argument the :named option means that this type is an acceptable "named
structure". With an argument. as in (:named typl'"" name). the symbol type-name should be that
name of some other structure type that defstruct should use if someone asks for the named
version of this type. (For example, in the definition of the :list type the :named option is used
like this: (:named :named-list).)
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Extensions to defstruct J42 NIL Manual
16.6.3.6 :keywords
"Inc :keywords option todefstruct-define-type. al10ws the user to define constructor
keywords (section 16.4.2. page 128) for this type of structurc. (For example the :make-array
constructor keyword for structurcs of type:array on Lisp Machines.) The syntax is:
( : keywordskeyword-I •.. keyword-n)
where each keYK'ord-i is a symbol that the constructor conser expects to find in the keywords alist
(section 16.6.3.1. page 139).
16.6.3.7 :dcfstruct -options
The :defstruct-options option to defstruct,..define-typeis similar to the :keywords option.
It is used to define new options that may appear in the options part of a defstruct for a structure
of this type. Its syntax is:
(:defstruct-options option-I ... option-II)
This defines each oplioll-j to be a option to defstruct that can he used with structures of this
lype. For example. tJ1e :array defstruct type for ih~ Lisp M,tchine uses the :defstruct-options
option as l(lllows:
(:defstruct-options :make-array)
Currently this just works by giving each option-; a non-nun :defstruct-option property (see
section 16.4.22. page 137). but soon it will check to be sure that each oplioll"; is 0111y used as an
oPtion with structures of this type.
16.6.3.8 :derstruct
The :defstruct option to defstruct-define-type allows the. user to run some code and return
some fonns as pan of the expansion of the defstruct macro.
The :defstruct option has the syntax:
( : defstruct (description)
body)
body is a piece of code that will be run whenever defstruct is expanding adefstruct fonn
that defines a structure of this type. The symbol description wilJ be bound to the instance of the
defstruct-descriptionstructure that defstruct maintains for this particular structure.
The value returned by the :defstruct option should be a list of fonns to be included with
those that the defstruct expands into. lous. if you only want to run some code at defstruct
expand time. and you don't want to actually output any additional code, then you should be
careful to return ni1 from the code in this option.
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16.6.3.9 :copier
The :copier option to defstruct-define-type allows the user to tell defstruct how to generate
the copier functions required by the :copier option to defstruct (section 16.4.10, page 134)~ This
option is entirely optional, because defstruct already has enough infonnation to write an adequate
copier function for any given type given the information supplied to the :ref and :cons options to
defstruct-define-type. However. it is sometimes desirable to teach defstruct a betfer way to
copy a particular type of structure.
The :copier option has the syntax:
( : cop i e r (descriptioll nomc)
body)
Similar to the :predicate option. dcscription is hound to the instance of the defstructdescription
structure maint~iined for this structure, name is bound to the symbol to be dcfined~
and bod)' is some code to e\'alu~lte to get the defining fonn. For example:
(:copier (description name).
t(defmacro ,name (x)
t(copy-frobboz .x)})
16.6.3.10 :implemcntations
The :implementations option to defstruct-define-type is primarily useful to the mainuliners
of defstruct in keeping control of the variations in defstruct types available in different
implementations. Its syntax is:
( : imp 1 ementati ons arg-I .•. arg-n)
'
This makes the defstruct-define-type in which it appears only take effect in
implementations of LISP in which (status feature arg-i) is true for at least one of the arg-i.
those
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The) .OOP Iteration Macro 144 Nil. Manual
17. The LOOP Iteration Macro
17. t Introduction
loop is a I.JSP macro which provides a programmable iteration facility. The same loop
module operates compatibly in LISP MACHJNE lJSP. MACUSP(PDP-lO and MCLTICS). and NIL. and
a moderately compatible package was developed for the MDL programming environment. loop
was inspired by the "FOR" facility of CLISP in INTFRL1~I); however. it is not compatible and
differs in several deLli1s.
The general approach is that a form introduced by the word loop generates a single program
J{)OP~ into which a large variety of features can be incorporated. The loop consists of some
initi,ltiltltion (pr%gue) code. a body which may be executed se\'cral times. and some exit
(epih,gue) code. Variables m~IY be dcchlred lncal to tJle loop. The features arc concerned with
loop variables .. deciding when to end tJle itemtion. putting user-written cude into the loop.
returning a vetlue from the construct. and iterating a variable through various real or virtual sets
of values.
The loop fonn consists of a series of chmses. each introduced by a keyword symbol. Forms
appearing in or implied by the clauses of a loop form are classed as those to be executed as
initialization code, body code. ,Uld/or exit code: within each part of the tcmplate that loop fins
in. they arc executed strictly in the order implied by the original composition. Thus. just as in
ordinarY l.isp code. side·effects may be used. and nne piece of cnde may depend on fhllowing
another filr its proper operation. This is tJ1C principal phiJosophy difference from I~TFRLlSP'S
"FOR" facility,
Note that loop forms are intended to look like stylized English rather than LISP code. There
is a not41bly low density of parentheses. and many of the keywords are accepted in several
synonymous fonns to allow writing of more euphonious and grammatical English. Some find this
notation verbose and distasteful, while others find it flexible and convenient. The fonner are
invited to stick to do.
Here are some examples to illustrate the use of loop.
(defun print-elements-of-list (list-of-elements)
{loop for element in list-of-elements
do (print element)}}
nil.
The above function prints each' element in its argument. which should be· a list It returns
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NIL Manual 145
Clauses
(defun gather-a1ist-entries (list-of-pairs)
(loop for pair in 1ist-of-pairs
collect (car pair»).
gather-alist-entries takes an association list and returns a list of the "keys":
(gather-alist-entries '«faa 1 2) (bar 259) (baz») returns (faa bar baz).
that is,
(defun extract-interesting-numbers (start-value end-value)
(loop for number from start-value to end-value
when (interesting-p number) collect number»
The ahove function takes two arguments. which should be fixnums. and returns a list of all
the numhers in that range (inclusive) which satisfy the predicate interesting-po
,(defun find-maximum-e1ement (an-array)
(loop fori from 0 below (array-dimension an-array 0)
maximize (aref an-array i»)
find-maximum-element returns the maximum of the clements of its argument. a onedimensional
array.
(defun my-remove (object list)
(loop for element in list
unless (equal object element)
my-remove is like tJle COM~10N LISP function remove. utilizing the equal predicate. (This is .
like MACLISP delete, but copies the list rather than destnlctively splicing out clements.)
(defun find-frob (list)
(loop for element in list
when (frobp element) return element
finally (ferror nil "No frob was found in the list -S"
list»)
This returns the first element of its list argument which satisfies the predicate frobp. If none
is found, an error is generated.
17.2 Clauses
Internally, loop constructs a prog which includes variable bindings, pre-jteration (initialization)
code. post-iteration (exit) code, the body of the iteration. and stepping of \'ariables of iteration to
. their next values (which happens on every iteration after executing the body).
A clause consists of the keyword symbol and any Lisp fonns and keywords which it deals
with. For example.
(loop for x in 1 do (print x».
contains two clauses. "for x in (car foo) It and "do (pr i nt x) ". Certain of the parte; of the
clause will be described as being expressions. e.g~ (car faa) in the above. An' expression is a
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single LISP form. Obviously. it must be followed immediately hy either the end of the loop fonn.
or by a loop keyword. Certain clauses take what is called a lIIulliple expression: this may be a
single LISP form. or a series of ronns implicitly co11ectcd with progn. A multiple expression is
terminated by the next following atom. which is taken to be a keyword. As a general rule. loop
clauses which utilize LISP forms deal only with single expressions. with the exception of those for
which the fonns are evaluated for effect: specifically. only the do, initiatty. and finally Clauses
allow multiple expressions.
This syntax differs slightly from earHer versions of loop (which arc prohably 5tiH in use in
I.lSP implementations other than J';JI). in which all expressions were treated as multiple
expressions. The reason for the change is twof(>ld: first. it common syntactic error in using loop
is to accidenta)J} omit the do keyword (causing the expressions meant to be executed for effcct to
h~come part of the preceding clause). Second. it is anticipated th41t loop will suppon ,Ill Itimplied
do" sometime in the future. making this omission in fact synt

NIL Manual 147 Clauses
(loop ... for y = illil then (9 x) for x = (f) ... )
because. as a general rule. parallel stepping has more overhead than sequential stepping.
Similarly. the example
(loop for sublist on some-list
and for previcius = 'undefined then sublist
· .. )
which is equivalent to the do construct
(do «sublist some-list (cdr sublist»
(previous 'undefined sU9list»
«null sublist) ... )
... )
in terms of stepping. would he hetter written as
(loop for previous = 'undefined then sub1ist
for sublist on some-list
· .. )
When iteration driving clauses are joined· with and. if the Loken following the and is not a
keyword which introduces an iterau.m driving clause. it is assumed to be the same as the keyword
which introduced the most recent clause; thus. the above example showing parallel stepping could
have been written as
(loop for sublist on some-list
and previous = 'undefined then sublist
uCl:au~c
· .. )
I..iac keyword ior is impiicd aftcr the and.
The order of evaluation in iteration-driving clauses is that those expressions which are only
evaluated once are evaluated in order at the beginning of the form. during the variablc-binding
phase. while those expressions which are evaluated each time around the loop are evaluated in
order in the body.
One common and simple iteration driving clause is repeat:
repeat expression
This evaluates expression (during the variable binding phase), and causes the loop to
iterate that many times. expression is expected to evaluate to a fixnum. If expression
evaluates to a zero or negative result. the body code will not be executed.
All remaining iteration driving clauses are subdispatches of the keyword for, which is
synonomous with as. In all of them a variable of iteration is specified. Note that, in general, if
an iteration driving clause imp1icitly supplies an cndtest, the value of this iteration variable as the
loop is exited (i.e., when the epilogue code is run) is undefined. (This is discussed in more detail
in section 17.6.)
Here are all of the varieties of for clauses. Optional parts are enclosed in curly brackets. The
dala-I),prs as lIsed hcre are discussed fully in section 17.4.
for \'ar {data-I)'pr} in exprl {by expr2}
This iterates over each of the clements in the list exprl. If the by subclause is
present, expr2 is e\'aluatcd once on entry to the loop to supply the function to be
used to fetch successive sublists. instead of cdr.
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for \'ar {dala-/J'f>f'} on eXl'rl {by ('xpr2}
This is like the previous for format. except that voris set to successive sublislc; of the
list instead of successive clements. Note that since var will always be a IisL it is' not
meaningful to specify a dala-t)'pe unless var is a deslruclurillg palferll, as described in
the section on deslruc/uring. page 158. Note a1so that loop uses a null rather than an
atom test to implement both this and the preceding clause.
for var {dala-type} = expr
On each iteration. expr is evaluated and var is set to the result.
for var {data-Iype} = exprl then expr2
l'(}r is hound to e.rpr/ when the loop is entered. imd set to ('xl'r2 (rc-e\',lluated) at all
hut the first iteration. Since exprl is e\'.tIUaled during the binding phase. it c~mnot
referenccolher iteration variables set before il~ fur that. usc the fullowing:
for \'ar {dtlld-IYfJl'} first ex!'r! then expr2
This' sets \'ar to ex})rl on the first iteration. and to ex!'r] (re"evaluated) on each
succeeding iteration. The evaluation of both expressions is . perfonned inside of the
loop binding environment. befl)re the loo'p body. This allows the first value of rar to
come from the first \';tlue of some other iteration \'ariah1c. allowing such constructs as
(loop for term in poly
for ans first (car term)
then (gcd ans (car term»
finally (return ans»
for r,;r (41&1:.; iypt) fiOin [xprl {to cxpr2} {by r..i.jlrJ)
This perfonns numeric iteration. var is initjalized to exp,l. and un each succeeding
iteration is incremented by expr3 (default 1). If the to phrase is given. the iteration'
tenninates whenvar becomes greater than expr2. Each of the expressions is eva1uated
only oncc. and the to and by phrases may be written in either order. downto may
be used instead of to. in which case var is decremented by the step value, and the
endtest is adjusted accordingly. If below is used instead of to. or above instead of
downto, the iteration will be tenninatcd before expr2 is reached, rather than after.
Note that the to variant appropriate for the direction of stepping must be used for the
endtesr to be fonned corrcctly; i.e. tbec04c will not work if expr3 is negative or
zero. If no limit-specifying clause is gi\'cn~then the direction of the stepping may be
specified as being decreasing by using downfrom instead of from. upfrom may also
be used instead of from; it forces· the stepping direction to be increasing. The datatype
defaults to fixnum. Thus. the idiom for stcpping through a typical COMMON USP
stan/end range in which the stan is inclusive and the end is exclusive, is
for var from SlaTt below end
for var {dat~type} being exprand its path ...
for var {da/a-type} being {eachlthe} path ...
This provides a user-definable iteration fhcility. path names the manner in which the
iteration is to be pcrfonned. The ellipsis indicates where various path dependent
preposition/expression pairs may appear. See the section on Iteration Paths (page 161)
for complete documentation~
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For binding more than one variable with no panicular initialization. one may usc the
construct
with variable-list {dala-type-list} {and ...}
as in
with (i j k tt t2) (fixnum fixnum fixnurn)
A slightly shorter way of writing this is
with (1 j k) fixnum and (tl t2) ...
These arc cases of deslru!'turillg which loop handles special1y; destructuring and data type
keywords are discussed in· sections 17.5 and 17.4.
Occasionally there are various implementationa] reasuns for a \'ariable 1101 to be given a local
type declar4ltioll. I f this is necessclry. the nodeclare clause may be used:
nodecfare rariubie-lisl
"111e variables in variable-iisl are noted by loop as not requiring local type declarations~
Consider the following: .
(declare (special k) (fixnum k»
(defun foo (1)
(loop for x in 1 as k fixnum = (f x) ... »
J f k did not have the 1ixnum data-type keyword given for it. then loop would bind it
to nil. and some compilers would complain. On the other hand. the fixnum keyword
also produces a local fixnum declaration filr k: since k is special. some compilers will
complain (or error out). The solution is to do:
(defun foo (l)
(loop nodeclare (k)
for x in 1 as k fixnum = (f x) ... »
which tells loop not to make that local declaration. The nodeclare clause must come
before any reference to the variables so noted. Positioning it incorrectly will cause this
clause 10 not take effect. and may not be diagnosed. It happens that this clause was
introduced due to some peculiar behavior of the MULTICS MACLISP compiler, and
should not be needed in other implementations.
17.2.3 Entrance and Exit
initially multiple-expression
This puts 11lUllipie-expression into the prologue of the iteration. It will be evaluated
before any other initialization code other than the initial bindings. For the sake of
good style, the initially dause should therefore be placed after any with clauses· but
before the main body of the loop. initially is one of the few loop clauses which are
allowed to be followed by multiple expressions; these expressions will be treated as an
implicit progn.
finaUy multiple-expression
Ibis puts multiple-expression into the epilogue of the loop, which is evaluated when
the iteration terminates (other than by an explicit return). For stylistic reasons. then,
this clause should appear last in the loop body. Note that cenain clauses may
generate code which tenninatcs the iteration without nmning the epilogue code; this
behavior is noted with those clauses. Most nowble of these are those described in the
section 17.2.7. Aggregated Boolean Tests. This clause may be used to cause the loop
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Clauses 152 Nil. Manual
cortecting ...
This causes the values of expr un each iteration to be collected into a list.
nconc expr {into var}
nconcing ...
append ...
appending ...
These are likecoltect. but the results are spliced together.
(loop for i from 1 to 3
nconc(list i (. i i»)
=> (1 1 2 4 3 9)
The diflercnce is that. for nconc. the value of ('xpris not copied oefore heing
spliced. not that the entire list being accumulated is repeatedly cop ted during the
iteration. This is significant in that one m,lyget ahold of the intennediate result while
the iteration is in progress by use of into, and lital list does get destructire!y modified.
count expr {into "or} {data-type}
counting ...
If expr evaluates non-nit a counter is incremented. The data-t)'p(' defaults to fixnum.
sum (').pr {dala-type} {into lIar)
summing ...
Evaluates expr on each iteration. and accumulates the sum of aU the values. dnla-t),pe
defaults to number. which for all practical purposes is notype. Note that specifying
dala-l),pe implies that both the sum and the number being summed (the value of
expr) will be of thattypc.
maximize expr {dala-t)pe} {into var)
minimize ...
Computes the maximum (or minimum) of expr over all iterations. data-type defaults
to number. Note that if the loop iterates zero times, or if conditionalization prevents
the code of this clause from being executed, the result will be meaningless. loop may
choose to code the max or min operation itself by just using arithmetic comparison
rather than calling max or min, if it deems this to be reasonable based on the
particular LISP implementation and the declared type of the accumulation. As with the
sum clause, specifying data-type implies that both the result of the max or min
operation and the value being maximized or minimized will be of that type.
Not only may there be multiple accumulations in a loop, but a single accumulation may come
from multiple places within the same loop Jonn. Obviously, the types of the collection must be
compatible. collect. nconc, and append may all be mixed. as may sum and count, and
maximize and minimize. For example,
(loop for x in '(a b c) for y in '«(1 2) (3 4) (5 6»
collect x
append y)
=> (a 1 2 b 3 4 c 5 6)
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Clauses
'Inc following computes the average of the entries in the list list-offrobs:
(loop for x in list-of-frobs
count t into count-var
sum x into sum-var
finally (return (quotient sum-var count-var»)
17.2.6 Endtests
The following clauses may be used to provide additional control over when the iteration gets
lenninaled. possihly causing exit code (due to finally) to be perfonned and possihly returning a
value (e.g.. from collect).
while expr
If expr evaluates to nil. the loop is exited. performing exit code (if any). and
returning any accumulated value. The test is placed in the body of the loop where it
is written. It may appear between sequential for clauses.
until expr
Identical to while (not e:rpr).
This may be needed. for example. to step through a strange data structure, as in
(loop for concept = expr then (superior-concept concept)
until (top-of-concept-tree? concept)
... )
lne following may also be of usc in terminating the iteration:
loop-finish
(loop-finish) causes the iteration to terminate "normally", the same as implicit tcnnination
by an iteration driving clause, or by the use of while or until-the epilogue code (if any)
will be run. and any implicitly collected result will be returned as the value of the loop.
For example.
(loop for x in '(1 2 3 4 5 6)
collect x
do (cond «= x 4) (loop-finish»»
=> (1 2 3 4)
This particular example would be better written as until (= x 4) in place of the do
clause. Also. the readability of loop constructs suffers from the inclusion of a nonkeyword
construct which affects the behavior of the iteration because the reader of the
code may not be expecting it hidden away in the code. (Stylistically it might be
compared with the use of go.)
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17.2.7 Aggregated Boolean Tests
All of these clauses pcrfonn some test.
depending on the result of that test.
and may immediately tcnninatc the iteration
aJways expr
Causes the loop to return t if expr always evaluates non-null. If expr evaluates to nil.
the loop immediately returns nil. without running the epilogue cod,c (if any. as
specified with the finally clause): otherwise, t will bc returned when the loop finishes.
after the epilogue code has been run.
never {'xpr
Causes the loop to return t if l'xpr never e"alu.ltes non-null. This is equivalent to
always (not ('xpr).
thereis expr
If rxpr cvaluates non-nil. then thc iteration is tenninatcd and that value is returned.
without running the epiloguc code.
17.2.8 ('onditionalization
These clauses may be used to tfconditionalize" the following clause. They may precede any of
the side-effecting or value-producing clauses. such as do. collect. always, Of return.
when expr
if expr
If expr evaluates to nil. the following clause will be skipped. otherwise not.
unless expr
This is equivalent to when (not expr».
1\.1ultiplc conditionalization c1auscs may appear in sequence. If one test fails, then any
following tests in the immediate sequence, and the clause being conditionalized, arc skipped. For
instance,
(loop for x ...
when (f x)
unless (g x)
do ••• )
is like
(loop for x •.•
when (and (f x) (not (g x»)
do ••• )
Multiple clauses may be conditionalilcd under the same test by joining them with and, as in
(loop fori from a to b
when (zerop (remainder; 3»
collect i and do (pr;nt i»
which returns a list of all mUltiples of 3 from a to b (inclusive) and prints them as they are
being collected.
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, I
I
I
!
I
NIL Manual 155
Clauses
If-then-else conditionals may be written using the else keyword. as in
(loop for i from a to b
when (oddp i)
collect i into odd-numbers
else collect i into even-numbers)
Multiple clauses may appear in an else-phrase. using and to join them in the same way as above.
There is a bug ill the handling of multiple else clauses. Beware.
Conditionals may be nested. For example.
(loop fori from a to b
when (zerop (remainder i 3})
do (print i)
and when (zerop (remainder i 2»
collect i)
returns a list of all multiples of 6 from a to b. and prints all multiples of 3 from a to b.
When else is llsed with nested condithmals. the "dangling else" ambiguity is resolved by
matching the else with the innennost when not already matched with an else. Here is a
complicated example.
(loop for x in 1
when (atom x)
when (memq x *distingu;shed-symbols*)
do (processl x)
~lse do (proc~ssZ x)
elsa when (memq (car x) *special-prefixes*)
collect (process3 (car x) (cdr x»
and do (memoize x)
else do (process4 x})
Useful with the conditionalization clauses is the return clause. which causes an explicit return
of its "argument" as the value of the iteration, bypassing any epilogue code. That is,
when exprl return expr2
is equivalent to
when exprl do (return expr2)
if the loop is not "named" (by use of the named clause), and to
when exprl do (return -from name expr2)
jf the loop is named name. In other words, return arranges to always return from the loop it is
a part of.
Conditionalization of one of the "aggregated boolean value" clauses simply causes the test
which would cause the iteration to tenninate early not to be performed unless the condition
succeeds. For example.
(loop for x in 1
when (significant-p x)
do (print x) (princ "is significant.")
and thereis (ext~a-special-significant-p x»
does not make the extra-special-significant-p check unless the significant-p check succeeds.
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Clauses 156 NIl. Manual
The fonnal of a conditionaJized clause is typically something like
when ('xprl k('yword exprl
Ifexpr2 is the keyword it~ then a variable is generated to hold the value of exprl. and that
variable gets substituted for exprl. Thus, the composition
when exprreturn it
is equivalent to the c1ause
thereis expr
and one may coBect all non-nuH values in an iteration by saying
when (':rpr('ssioll collect it
If multiple clauses arc joined with and. the it keyword m,l), only be lIsed in the first. If multiple
whens. unless('s. and/or ifs occur in sequence. the \'alue suhstituled for it will he thilt of the last
tl'Sl perf(mncd. The it keyword is not rccogni/ed in an else-phmsc.
17.2.9 l\1isceUaneous Other ('Iauses
named nal11(,
This gives the block (prog) which loop generates a name of name, so that one may
usc the return-from fonn lo return explicitly out of thal particular loop:
(loop named sue
do (loop ... do (return-from sue value) 0 00 )
... )
1'h(' return -from fnnn ~h(n."n C~!.!$CS va!::[' to b~ !mmcdiat~!y rcturn~d a5 :..~c value of
the otHer loop. Only one name may be given to any particular loop constmct. This
feature docs not exist in the MACLlSI' version of loop. since MACUSP docs nol suppon
"named progs" or COMMOl" LISP ,blocks.
return expression
Immediately returns the value of expression as the value of the loop~ without running
the epilogue code. This is most useful with. some son of conditionaJization. as
discussed in the previous section. Unlike most of the other clauses, return is not
considered to "generate body code'\ so it is allowed to occur between iteration
clauses. as in
(loop for entry in list
when (not (numberp entry»
return (errol" ..• )
as frob = (times entry 2)
... )
If one instead desires the loop to have some return value when it finishes nonnally t
one may place a ca11 to retum or return-from (as appropriate) in the epilogue (with
the finally clause. page 150). return always returns from the loop it is a pan of; that
is, it turns into a call to return if the loop is not "named", return-from if it is.
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N ll. Manual 157 I.oop Synonyms
17.3 Loop Synonyms
define-loop-macro keyword
May be used to make keyword. a loop keyword (such as for). into a Lisp macro which
may introduce a loop form. For example. after evaluating
(define-loop-macro for),
one may now write an iteration as
(for; from 1 below n do ... )
This facility exists primarily for diehard users of a predecessor of loop. Its unconstrained usc
is not recommended. as it tends to dCl'rease the transportahility of the code and needlessly uses
up ~I function n

Dcstructuring 158 Nil. MJnual
number
notype
Any number.
Unspecified type (i.e.. anything else). This name is inherited from MACLISP.
Note that explicit specification of a non-numcric type for an operation which is numeric (such
as the summing clause) may cause a variable to be initializcd to nil when it should be O.
If local data-type declarations must be inhibited. one can usc the nodecfare clause. which is
described on page 150.
17.5 Dcstructuring
IJrstrucluring provides one with the ability tu "simultaneollsly" assign or bind multiple
v(lriablcs to components of some data structure. Typically this is used with list stnJcture. For
example,
h~ls
(loop with 1foo . bar) = 'ea b c) .. 0)
the effect of binding foo to a and bar to (b c).
loop's destructuring support is intendcd to parallel if not augment that provided by the hust
LISP implementation. with a goal of minimally providing destructuring over Jist structure patterns.
Thus, in I -isp implementations with no system dcstructuring support at all. one may still usc liststructure
patterns as loop iteration variables, and in with bindings. In NIL, loop also supports
dcstrucIUring over vectors (they should be general vecto~ Le .. have element-typet).
One may specify the data types of the components of a pattern by using a corresponding
pattern of the data type keywords in place of a single data type keyword. This syntax remains'
unambiguous because whcrever a data type keyword is possible. a loop keyword is the only other
possibility. Thus. if one wants to do
(loop for x in 1
as i fixnum = (car x)
and j fixnum = (cadr x)
and Ie fixnum = (cddr x)
•• 0 )
and no reference to x is needed, one may instead write
(loop for (i j . Ie) (fixnum fixnum . fixnum) ;n 1 ••• )
To allow some abbreviation of the data. type pattern, an atomic component of the data type
pattern is considered to state that all components of the corresponding part of the variable pattern
are of that type. That is, the previous form could be written as
( 1 00 p for (i j . Ie) fix n urn i n 1 • 0 • )
This generality allows binding of multiple typed variables in a reasonably concise manner, as in
(loop with {a b c) and (i j k) fixnum .. 0)
which binds a. b, and c to nil and i. j. and k to 0 for use as temporaries during the iteration.
and declares i .. j, and k to be fixnums for the benefit of the compiler.
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NIl. Manual 159
The Iteration Framework
(defun print-with-commas (list)
(loop for (item. more?) on list
do (princ item)
when more? do (prine ". H»~)
wi1l generate the output
Foo, Bar. Baz
when called on the list ("Faa" "Bar" ttBaz").
In I.lSP implementations where loop perfonns its own destrucluring. notably MUITlCS MACUS}>
and IISP ~1ACIII'I: liSP. one can cause loop to liSt' already prodded destrllcturing support
instead:
51: loop-u5e-5ystem-de5truetur1ng? Variable
This variable only exists in loop implementations in LISPS which do not provide
destruclllring support in the default environment. It is by default nil. If changed, then
loop wi'l behave as it docs in I.lSPS which do provide dcstructuring support: destructuring
binding will be pcrfi)rmed llsing let. and destructuring assignment will be perfonned llsing
desetq. Presumably if one's personalized environment supplies these macros, then one
should set this variable to t~ there is, however, little (if any) efficiency loss if this is not
done.
17.6 The It£lr:ltion Framework
This section describes the way loop constructs iterations. It is necessary if you will be writing
your own iteration paths, and may be useful in clarifying what loop docs with its input
loop considers Ille act of stepping to have four possible parts. Each iteration-driving clause
has some or all of these four parts, which are executed in this order:
pre-step-endtest
This is an endtest which detennines if it is safe to step to the next value of the
iteration variable.
steps
Variables which get "stepped". This is internally manipulated as a list of the fonn (varl
vall var2 val2 ... ); all of those variables arc stepped in paranel. meaning that all of the
vals arc evaluated before any of the vars are set
post-step-endtest
Sometimes you can't see if you are done until you step to the next value; that is, the
endtest is a function of the stepped-to value.
pseudo-steps
Other things which need to be stepped. lbis is typically used for internal variables
which arc more conveniently stepped here. or to set up iteration variables which are
functions of some internal variablc(s) which arc actually driving the iteration. This is a
list like steps, but the variables in it do not get stepped in parallel.
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"I'he ltermion Framework . 160 NIL Manual
The ahove alone is actuafly insufficient in just about all iteration dri\ ing clauses which loop
handles. What is missing is that in most cases the stepping and testing fhr the first time through
the loop is different from that of aJJ other times. So. what loop deals with is two four-tuples as
above; one for the first iteration. and one fhr the rest. The first may be thought of as describing
codc which immediately precedes the loop in the prog. and the second as following the body
code-in fact. loop docs just. this. but severely perturbs it in order to reduce code duplication.
Two lists of fonns arc constructed in parallel: one is the first-iteration endtests and steps, the
other the rcmaining,:,iterations endtests and steps. These lists have dummy entries in them so that
identical expressions will appe.lr in the scmle position in both. When loop is done parsing an of
the clauses. these lists gel merged bark wgether such that corresponding identical expressions in
hoth lists arc not duplicated unless they arc "simplc" and it is worth doing.
Thus. one lIIay get some duplicated code if one lias multiple iterations. Alternatiyely. loop
may decide to usc and test a flag variable which indicates whether one iteration has been
perfonned. In genera1. sequential itcrations have less (}\·crhcad th.m parallel iterations. both from
thc inhercnL overhead of stepping multiple variables in parallel. and from thc s14mdpoint ·of
potentia) code duplication.
One other point which must be notcd ahout pclrallc1 stepping is that although thc user
iteration variables arc guarantecd to be stepped in parallcl. the placement of the endtcst for any
particular iteration may bc either before Of after the stepping. A notable casc of this is
(loop for i from 1 to 3 and dummy = (print 'fool
collect i)
_.... I.. '\ ., '\
-, \.a. c. v J
but prinl~ foo four times. Certain other constructs. such as for l'ar on. mayor may not do this
depcnding on the particular construction.
This prohlcm also means that it may not be Stlfe to examine an iteration variable in the
epilogue of the loop fonn. As a general rule, if an iteration driving clause implicitly supplies an
endtest. then one cannot know the state of the iteration variable whcn the loop tcnninatcs.
Although one can guess on the basis of whether the iteration variable itself holds the data upon
which the endtest is based. that guess may be wrong. Thus.
(loop for subl on expr
finally (f subl»
IS Incorrect. but
(loop as frob = expr whi le (g frob)
finally (f frob»
is safe because the endtest is explicitly dissociated from the stepping.
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.'t'fnc ; mtfrM rt'¥?9 an Tf N '" T" at' , 7thM ~'{ rt t inea@-'"
;'@ rtr$v'xYtc ,""'.nV? cn -u
NIL Manual 161 Iteration Paths
17.7 Iteration Paths
Iteration paths provide a mechanism for user extension of iteration-driving clauses. The
interface is constrained so that the definition of a path need not depend on much of the internals
of loop. The typical fonn of an iteration path is
for var {data-type} being {eachlthe} palhname {preposilionJ exprJ} ...
pathname is an atomic symbol which is defined as a loop path function. The usage and
defaulting of data-type is up to the path function. Any number of preposition/expression pairs
may be present: the prepositions allowable for any particular path are defined by that path. For
example.
(loop for x being the elements of some-sequence from 1 to 10
· .. )
To enhance readability. iteration path names are usually defined in both the singular and plural
fnnns: this particular example could h,lve been written as
(loop for x being each element of some-sequence from 1 to 10
· .. )
Another fonnat. which is not so generally applicable. is
for l'ar{data-I),pc} being exprO and its path-name {prcposiliolll exprl} ...
In this fonnat. var wkes on the value of exprlJ the first time through the loop. Support for this
fonnat is usually limited to paths which step through some data structure. such as the "superiors"
of something. Thus, we can hypothesize the cdrs path, such that
(loop for x being the cdrs of '(a b c . d) collect x)
~; «b C . d) (c . d) d)
but .
(loop for x being '(a b c . d) and its cdrs collect x)
=> «a be. d) (b c . d) (c . d) d}
To satisfy the anthropomorphic among you, his. her. or their may be substituted for the its
keyword. as may each. Egocentricity is not condoned. Some example uses of iteration paths arc
shown in section 17.7.l.
Very often. iteration paths step internal variables which the user does not specify. such as an
index into some data-structure. Although in most cases the user docs not wish to be concerned
with such low-level matters, it is occasionally useful to have a handle on such things. loop
provides an additional syntax with which one may provide a variable name to be used as an
"internal" variable by an iteration path, with the using "prepositional phrase". The using phrase
is placed with the other phrases associated with the path, and contains any number of
keywordh ariable-name pairs:
(loop for x being the elements of seq using (index i)
· .. )
which says that the variable i should be used to hold the index of the sequence being stepped
through. The panicular keywords which may be used are defined by the iteration path; the index
keyword is recognized by all loop sequence paths (section 17.7.1.2). Note that any individual
using phrase applies to only one path; it is parsed along with the "prepositional phrases". It is
an error if the path docs not call for a variable using that keyword.
By special dispensation, if a path-name is not recognized. then the default-loop-path path
will be invoked upon a syntactic transfonnation of the original input. Essentially. the loop
fragment
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Iteration Paths
162
NIL Manual
for var bei ng frob
is taken as if it were
for var being default-loop-path in frob
and
for var bei ng expr and its frob •••
is taken as if it were
for var being expr and its default-loop-path in frob
Thus, this "undefined path-name hook" only works if the default-loop-path path is defined.
Ohviously. the usc of this "hook" is competitive. since only une such hook may be in usc, and
the potential for syntactic amhiguity exists if frob is the name of a defined iteration path. 'Ibis
feature is not f()f casual usc: it is intended for usc by large systems which wish to usc a special
SyntilX for some fealUre tJley provide.
17.7.1 Pre-Defined Paths
loop comes with two pre-defined iteratinn pat~ functions: one implements a mapatoms-like
iter.,tion path facility_ and the other is used for defining iteration paths for stepping through
sequences.
17.7.1.1Thc Interned-Symbols Path
The interned -symbols iteration path is like amapatoms (or COMMO!\ LISP do-symbols) for
loop.
(loop for sym being interned-symbols ... )
iterates over all of the symbols in the current package and its superiors (or. in' Maclisp. the
current obarray). This is the same set of symbols which mapatoms iterates over, although not
necessarily in the same order. The particular package to look in may be specified as in
(loop for sym being the interned-symbols in package ••• )
which is like giving a second argument to mapatoms.
In LISP implementations with some son of hierarchical package structure such as USP
MACHINE USP and NIl; one may restrict the iteration to be over just the package specified and
not its superiors, by using the local-interned -symbols path:
(loop for sym being the local-interned-symbols {in package}
... )
Example:
(defun my-apropos {sub-string &optional (pkg package»
(loop for x being the interned-symbols in pkg
when (string-search sub-string x)
when (or (boundp x) (fboundp x) (plist x»
do (print-interesting-info x»)
In the LISP MACHINE USP and NIL implementations of loop. a package specified with the in
preposition may be' anything acceptahle to the pkg-find-package function. The code generated
by this path will comain calls ((l internal loop functions. with tJ1C CtfL'Ct that it will be transparent
to changes to tJle implementation of packages. In the MACf .ISP implementation. the obarray must
be an array pointer. not a symbol with an array propeny.
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NIL Manual 163 Iteration Pallls
17.7.1.2 Sequence Iteration
One very common fonn of iteration is that over the c1ement~ of some object which is
accessible by means of an integer index. loop defines an iteration palll function for doing this in
a general way, and provides a simple interface to allow users to define iteration paths for various
kinds of "indexable" data.
def1ne-loop-sequence-path
(def i ne-1 oop-sequence-path palh-llame-o~lIames
fe/ch-full size-full
.\"('ljucllc('-Iype dcfiJu!t-wu'-type)
l'olli-lIt1I11C-O""I/(//II('s is either an atomic p~tth name or list of path names. fe/ch-full is a
function of two arguments: the sequence. and the index of the item to be fetched.
(Indexing is asslImed to he lero-origined.) si:c-/im is a function of one argument. the
~eqllence: it should return the number of clements in the sequence. sequel1ce-type is the
name of the data-type of the sequence, and dljGu/t·l'a,. .. t),pe the name of the data-type of
the clements of the sequence. These last two items are optional.
The ~IL implementation of loup utilizes the COMMO!' LISP sequence manipulation primitives
to define both element and elements as iteration paths:
(define-loop-sequence-path (element elements)
elt length)
Then. the loop clause
f',,1" .".,r nn; nn
#'>",....,,, ... ,..,,,
• ...,. • .... w ........ ~ the clements of .n "1"'(. III C.
will step var over the clements of sequence. starting from O. The sequence palll function also
accepts in as a synonym for of.
The range and stepping of the iteration may he specified with the use of all of the same
keywords which are accepted by the loop arithmetic stepper (for var from ... ); they are by, to,
downto. from, downfrom, below, and above, and are interpreted in the same manner. Thus,
(loop for var be; n9 the e1 ements of sequence
from 1 by 2
... )
steps var over all of the odd clements of sequence, and
(loop for var be; ng the el ements of sequence
downto 0
... )
steps in "reverse" order.
The NIL implementation of loop defines the following additional sequence iteration paths.
Basical1y, they are all special cases of the general elements path, but can generate better code
because they may know how to access the sequence better. (If NIL's compiler were smarter, one
would be able to get the same effect willl type declarations. but that is not the case yet.) Each
iteration path name is defined in both the singular and plural fonn.
vector-elements
This will iterate over any type of vector. There really isn't a good reason to lise this
over the elements iteration path anymore.
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characters
string -elements
This iterates over the characters of a string. char is used to reference them. hence
the iteration variable defaults to type string-char.
bits
bit - vector-elements
This iterates over the bits in a bit-vector: the iteration variable is declared to be bit,
as it can take on only 0 or 1 . as values.
The following arc the special cases which m~ly be of somewhat more intercst. because they
can generate much bener code kl~(}wing that the sequence is of it pankular simple type:
simple-vector-elements
The sequence must be a simp1c lector.
simple -string - elements
The sequence must be a simple string.
sim~: ~ - bit - vector-elements
The sequence must he a simple bit vcctor.
An such sequcnce iteration paths allow one to specify the variable to be used as the index
variable. by use of the index keyword with the using prepositional phrase. as described ( with an
example) on page 161.
17.7.2 Defining Paths
This section and the next may not be of interest to those not interested in defining their own
iteration paths.
A loop iteration clause (e.g. a for or as clause) produces. in addition to the code which
defines the iteration (section 17.6), variables which must be bound~ and pre-iteration (prologue)
code. This breakdown allows a user-interfacc to loop which docs not have to depend on or know
about the internals of loop. To complete this separation. the iteration path mechanism parses the
clause before giving it to the user function which will return those items. A function to generate
code for a path may be declared to loop with the define-loop-path function:
define-loop-path
(dafi ne-l oop-path palh·flame-o~names path-function
Iisl-ofallowable-prepositions
datum- J datum- 2 ••• )
This defines palh-/ullClioll to he the handler for the path(s) path-Ilame-or-names. which
may be eithcr a symbol or a list of symbols. Such a handler should fonow the
conventions described below. The datum-; are optional; they are passed in to pathfunc/ioll
asa list
The handler will be caned with the following arguments:
path-Ilame
The name ofth.e path which caused the path function to he invoked.
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Nil. Manual 165 heration Paths
l'ariable
'1l1e "iteration variable".
data-type
'Ibe data type supplied with the iteration variable, or nil if none was supplied.
prepositional-phrases
'Ibis is a list with entries of the fonn (preposition expression). in the order in which
they were collected. This may also include some supplied implicitly (e.g. an of phrase
when the iteration is inclusive. and an in phrase for the default-loop-path path): the
ordering will show the order of evaluation which should be followed for the
expressions.
inclusive?
'Ibis is t if variable should have the starting point of the path as its value on the first
iteration (by virtlle of being specified with syntax like for l'elf being expr and its
pal/mallu'). nil otherwise. When t, expr will appear in prepositiunal-phrases with the
of preposition: for example. for x being faa and it~i cdrs gets prepositional-phrases
of «of faa».
allowed-preposi t iOlls
'1l1is is the list of allowable prepositIOns declared for the pathname that caused the
path function to be invoked. It and data (immediately below) may be used by the
path function such that a single function may handle similar paths.
data
This is the list of "data" declared for the pathname that caused the path function to
be invoked. It may. for instance. contain _ a canonicalized pathname, or a set of
functions or flags to aid the path function in determining what to do. In this way,
the same path function may be able to handle different paths.
The handler should return a list of either six or ten clements:
variable-bindings
This is a list of variables which need to be bound. 'The entries in it may be of the
fonn variable. (variable expression). or (variable expression data-t)pe). Note that it is
the responsibility of the handler to make sure the iteration variable gets bound. All of
these variables will be bound in parallel; if initialization of one depends on others. it
should be done with a setq in the prologue-fonns. Returning only the variable
without any initialization expression is not allowed if the variable is a destructuring
pattern.
prologue-Jorms
This is a list of fonns which should be included in the loop prologue.
the four items of the iteratioll specification
These are the four items described in section 17.6. page 159: pre-step-endtest. steps,
posr-slep-endtest, and pseudo-steps.
another Jour items of iteratioll specification
If these four items are given. they apply to the first iteration. and the previous fOllr
apply to all succeeding iterations; otherwise, the previous four apply to all iterations.
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Iteralion Paths 166 N II. Manual
Here are the routines which are used hy loop to compare keywords for equality. In all cases.
a /okcll may he any LISP object. but a keytwJrdis expected to be an atomic symbol. In cerwin
implementations these functions may be implemented as macros.
s 1: 1 oop-tsqual token keyword
This is the loop token comparison function. token is any Lisp object; keyword is the
keyword it is to be compared against.· It returns t if they represent the same token.
comparing in a manner appropriate for the implementation.
51: loop-tmember lokell keyword-lisl
The member variant of si:loop-tequal.
s1 : 1 oop-tas soc /OkCI1 keyword-alisl
The assoc \'ariant of si:loop-tequal.
The followiilg macro turns into the "proper" cude for generating a temporary variable in a
particular I.ISP implementation.
51: loop-gentemp &optional prcfi~r
This expands into a call to the proper function for constructing a temporary variable.
Depending on how it expands. the form prefix may not get used (so it should not have
interesting side effects!). In Nil. (and eventually in some other implementations). this
utilizes the gentemp function so that the generated variable wi1l be interned and
somewhat mnemonic: in this case. . nrefix ... (which should he Ii ~vmhnl .,.""", nr Ii "rrino\ will .... hp
used as a prefix of the generated symbol. In other implementations. si:loop-gentemp
will expand to just a call to gensym. and throwaway prefix.
If gentemp docs get used but prefix is not supplied, then the prefix loopvar- is used so
that the variable is identifiable as originating with loop.
If an iteration path function desires to make an internal variable accessible to the user, it
should call the following function instead of si:loop-gentemp:
s1 :loop-named-var1ab18 keyword
This should only be caned from within an iteration path function.· If keyword has been
specified in a using phrase for this path, the corresponding variable is returned;
otherwise. si:loop-gentemp is caned and that new symbol returned. Within a given path
function. this routine should only be caned once for any given keyword.
If the user specifics a using preposition containing any keywords for which the path
function does not caU si:loop-named-variabte. loop will infonn the user of his error.
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NIL Manual 167 Iteralion P"llls
17.7.2.1 An Example Path Definition
Here is an example function which defines the string -characters iteration path. This path
steps a variable through all of the characters of a string. It accepts the fonnat
(loop for var bei ng the stri ng-characters of sir ... )
The function is defined to handle the path by
{define-loop-path string-characters string-chars-path
(of»
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Iteration Paths 168
Nil. Manual
Here is the function:
(defun string-chars-path (path-name variable data~type
prep~phrases inclusive?
allowed-prepositions data
&aux (bindings nil)
(prologue nil)
string-var
index-var
size-var)
(declare (ignore allowed-prepositions data»
(setq string-var (si:loop-gentemp 'loop-string-)
index-var (si:loop-gentemp 'loop-index-)
size-var (si:1oop~gentemp 'loop-size-»
To iterate over the characters of a string. we need
to save the string. sav~ the size of the string.
step an index variable through that range, setting
the user's variable to the character at that index.
Default the data-type of the user's variable:
(cond «null data~type) (setq data~type string-char»)
; We support exactly one "prepOSition", which is
; required, so this check suffices:
(cond «null prep-phrases)
(ferror nil "OF missing in -S iteration pat~ of -5"
pa t h-name va r i ab 1 e) ) ) .
; We do not support "inclusive" iteration:
(cond «not (null inclusive?»
(ferror nil
"Inclusive stepping not supported in -S path -
of -S (prep phrases c -:S)"
path-name variable prep-phrases»)
; Set up the bindings
(setq bindings {list (list variable nil data-type)
{list string-val' (cadar prep-phrases»
(list index-val' 0 'fixnum)
(list size-var 0 'fixnum»)
; Now set the size variable
(setq prologue (list '(setq ,size-val' (string-length
,string-var»»
; and return the appropriate stuff, explained below.
(list bindings
prologue
t(= ,index-val' .size-ver)
nil
nil
(list variable '(char ,string-val' ,index-val')
index-var '(1+ ,index-var»»
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Nil. Manual 169 Iteration Paths
The first clement of the returned list is the bindings. The second is a list of forms to be
placed in the prologu('. The remaining clements specify how the iteration is to be perfonned.
This example is a particularly simple case, for .two reasons: the actual "variable of iteration".
index-var. is purely internal (being gensymmed). and the stepping of it (1 +) is such that it
may be perfonned safely without all endtest. Thus index -var may be stepped immediately· after
the setting of the user's variable. causing the iteration specification for the first iteration to be
identical to the iteration specification for all remaining iterations. This is advantageous from the
standpoint of the optimizations loop is able to perfonn. although it is frequently not possible due
to the semantics of the iteration (e.g.. for l'ar first ('xpr! then ('xl'r2) or to subtleties of the
stepping. It is safe filr this path to step the user's variable in the ps('udo-sl('ps (the fourth item of
an iteration specification) rather than the "real" steps (the second). because the step vallie C(lll
have no dependencies on any other (user) iteration vari41bles. Using the pseudo-steps generally
results in some cflicicncy gains.
I f one desired the index variable in the above definition to be user-accessible through the
using phrase feature with the index keyword. the function would need to be changed in two
ways. First. index-var should be set to (si:loop-named-variable 'index) instead of the call to
si:loop-gentemp. Secondly. the efficiency hack of stepping the index variable ahead of tie
iter~tion variable must not be done. This is effected by changing the last fOim to be
(list bindings prologue
nil
(list index-var '(1+ ,index-var»
'(= ,index-var ,size-var)
(list variable ~(char ,string-~ar .1naeX-Var),
nil
nil
'(= ,index-var ,size-var)
(list variable '(char ,string-var ,index-var»)
Note that although the second '( = ,index-var ,size-var) could have been placed earlier (where
the second nil is). it is best for it to match up with the equivalent test in the first iteration
specification grouping.
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The Flavor Facility 170 NIL Manuill
18. The Flavor Facility
IS. 1 Introduction
Languages such as Smalltalk and Act-1 are designed to encourage a style of programming
called object-oriented programming. LISP MACIIIJl.:E LISP offers a facility for object-oriented
programming as well: it is caHed the Flavor System. or just flavors. NIl. offers a more primitive
version of flavors than is available on the l.isp Machine. but unless you do quite complicated
things with flavors. you will probably never notice the difference.
18.1.1 Object -oriented Programming
Suppose you were writing a file system. You might have several different types of files.
including. for example. binary files and text files. If you wrote a program to print files on a
user"s tenninaJ. and you wanted it to print ASCII characters when the user printed a text file. but
ncwl numbers when the user printed a binary file. you might implement it as fonows:
(typecase file
(binary (octal1y-print file»
(text (ascii-print file»)
That is. you might dispatch off the type of the file, calling the appropriate function to print the
file. It might be nicer. however. to keep the infonnation about how the file should be printed
with Ihe fill' itself. 'J11at is. the method used for printing itsclfcould be part of the int(>rmation
contained in each file: we could simply decide that every type of file we will support in our
operating system will know how to perform certain operations. and we could specify printing on a
tenninal to be one of them. Then we would implement the above as
(send file :print-contents)
where :print-contents is ·the name of a method that could be specified for each type of file.
On simply looking at the differences between the two samples of code, one might notice that
the second expresses much more clearly and compactly what we are doing: printing the file. We
trust whoever defined this type of file object to have defined a reasonahle :print-contents method
for it. and we don't worry any further about type-dispatching and the like. Thus object-oriented
programming constructs can have the effect of fre~ing the programmer from an extra level of
detail.
This should sound familiar even to users who have not used flavors. because it is similar to
generic arithmetic in COMMO~ LISP. In fact. operations that work for more than one type of
object (like the imaginary :print-contents above) are called generic operations.
Another thing we might notice about the object-oriented way of doing things is described by
its name. We might say somewhat fancifully that the files in our example above have been raised
from the realm of "inanimate data· J
to being objects that can do things. A file has become an
object thal knows how to print itself. and can be asked to do so.
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NIL Manual 171 Introduction
Ohjects can know of things besides their methods for perfonning operations, and this brings
up another advantage of object-oriented programming, which is useful even when one is not
planning on implementing operations that will work on a large class of objects. Two objects of
the same type will share the same methods for perfonning an operation. But two objects· of the
same type can still have distinct state. They can have instance variables: variables that are local
to each instantiation. in much the same way that scoped variables arc local to a function call.
For example. the file objects we were discussing above could have variables :author and :writedate.
and each object would have its own value for these variables.
18.1.2 Object-oriented Programming llsing Flavors
When we lise flanlrs to write object-oriented code. the objects themsehes are not flavors.
They are ills/mr/ia/iolls of flavors. The flavor of an object is actually its type. We define a flavor
using ~efflavor. The definition of a flavor looks like
(defflavor flavor-name installce-variables
com l'ol1cl1/~flavors
optionl option2... )
The flavor-namc can be any symhol. the ills/ancc-variables a (possibly nu11) list of symbols
(variables) and their initial values. the component-flavors a list of flavors. and the options will be
described further helow. A more concrete example is:
(defflavor bicycle «wheel-size nil) (gear-ratios nil)
(s~l~ct~d-gear nil)
(distance-travelled nil»
( )
:gettab1e-instance-variables
:settable-instance-variab1es)
The option :gettable-instance-variables will cause a method that will return the value of
that instance variable to be defined for each of the instance variables. :settable-instancevariables
will cause a method that will allow us to set the value of that instance variable to be
generated for each instance variable.
If we want to create an instantiation of the flavor bicycle, we use make-instance:
(setq my-bike (make-instance ·bicycle»
returns
#
or something like it This object can be described:
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Introduction 172 NIL Manual
(describe my-bike)
The instance at address 128788 is of flavor BICYCLE and is 4
Q's long. It directly or indirectly includes flavors (BICYCLE
VANILLA-FLAVOR), and is of the types (BICYCLE VANILLA-FLAVOR).
The 4 instance variables are:
WHEEL-SIZE NIL
GEAR-RATIOS NIL
SELECTED-GEAR NIL
DISTANCE-TRAVELLED NIL
NIL
We can calise an instiHlllatlOn of &1 flanlr to execute ,I method with send. The mctllods
LT~ated upon definition of a flavor with the option :settable-instanee-variables ha\e the n~lfncs
of the instance \'ariables appended (0 "set·n
, but are in tllC keyword package. Thus we could set
lhe value of wheel -size like tllis:
(send my-bike :set-wheel-size 27) .
The methods created on definition of a ftil\'Or with the option :settabfe-instance-variables are
the same ~IS the names of the variahles. but are in the keyword paCkitge. So we could get the
,'arlle of :wheel-size like this:
(send my-bike :wheel~size)
27
send objcct message &rest args
This is the basic message-passing primitive. It should be used instead of funeaU. which
has been used in the past in LISP MACIUNE LISP.
1 expr-send o~iecl message &rest args
This is to send as lexpr-funeall (which is apply (page 31). as it is defined now) is to
funeaU.
There must be at least one arg given~ and the last one must be either a list or a vector.
The object is sent message with arguments of all of the other args followed by all the
elements of the last arg.
send-forward object message {arg}-
This is only valid within the lexica1 scope of a defmethod definition.
Let the flavor which this method was defined on be caned jlav. send-forward then does
a s~nd, but stans searching for methods to handle message after jIav.
n.b. send-forward is neither as efficient as it should be nor as efficient as one would like.
yet. Note that it can be used 10 acheive many of the same effects as method combination.
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NIL Manual 173
Introduction
1 expr-send-forward ()~iecl message {arg}*
Like lexpr-send. but does send-forward.
mak.e-i ns tance jla\'o~llame &rest keyworded-argumel1ts
This is the primary instantiation function. The keyworded-argumellls arc alternating
keywords and values. Typically, they specify initial values for the instance variables which
arc initable (as specified with the :initable-instance-variables option to defflavor). '1l1ey
may also be arbitrary keywords which are checked for validity against those specified with
the :init-keywords option to defflavor. which (merged with the :init-piist specification to
defflavor) will be passed as arguments to the :init method of the flavor.
deffl avor jlcl\'UI~l1ame
illslallce-varhlbles illc/uded-jlm'ors oplions ..•
flawr-nlll1ll' is the name of the flavor being defined. After it is defined. it is acceptable as a
second argument to typep (page 18), which will return t if given a second argument of flavor­
Ilame and a first argument of an instantiation of jlayo""llwl1e. or any other flavor which directly or
indirectly includes jla\'o~l1all1e.
iIlS/Llllce- rariablcs is a list of inswnce variables or lists of instance variables and forms to e\'al
to ohtain their initial values. These arc not necessarily all of the instance variables of the
instance: some may be inherited from other flavors which jlavor-name is being built from.
However. compiled flavor methods for jlavor-name may not know about those inherited instance
variables. so if you "know" that a flavor is going to have certain variables and need to use them.
Y01l c;h(\t'~d inc1udr them h('r~. (Note that in the current ~:!!. !ns~ncc '."3:-bh1~ inh~r!tmcc is
perfonlled when the defflavor form is compiled. so one will not receive a diagnostic about this.
The inheritance will be deferred in in some later release. however. to provide for other features.
including the ability to not have the component flavors of flavor-name defined when the defflavor
is being compiled or interpreted.)
If an atomic instance variable is specified in the instance variables list. then the instance
variable is initialized "unbound" by make-instance (assuming no initiaHzation was specified with
make-instance). This will cause an unbound variable reference in the 1\IL interpreter; external
("outside accessible") references will just pick out the unbound pointer. as will compiled
references to the instance variable, and probably cause some spastic behavior later.
Otherwise, the instance variable specification should be a list of the ins~1nce variable and an
initialization fonn, which will be evaluated to determine the initial value. (NIL actually does not
use eval, but stores the value either as a constant, if it self-evaluates, or as a function of no
arguments which evaluates the initialization form; this function will be compiled when the
defflavor fonn is compiled.)
The following defflavor options all deal with instance variables which must be listed in the
instance-variables given for the defflavor. They may appear as atomic options, like :gettableinstance-variables
and :settable-instance-variables in the bicycle example (page 171). in
which case they refer to an of the instance-variables of the defflavor, or listed with those hey
pertain to, as in
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Introduction 174
Nil. Manual
(defflavor frob (var-l var-2 var-3) ()
:gettable-instance-variables
(:settable-instance-variables var-l var-2»
in which var-1. var-2. and var-3 are all :gettable. but only var-l and var-2 are :settable.
:gettable- instance - variables
Causes automatic generation of methods which will· fetch the values of the specified
instance variables. ...:ach method name is the name of thc variablc interned in the
keyword package. Thus in the bicycle eX&lmple. one may send a bicycle the :distancetravelled
message to find how far the bicycle h

---_.-._-----_.
NIL Manual 175 Introduction
one. and make-instance is supposed to barf if that is not the case.
:required - methods
Any flavor including this flavor is required to support the listed methods. This is alledgely
checked ell instantiation time.
:no-vanilla -flavor
Do not include vanilla -flavor. as is done by default.
:included- flavors
Sort of like building the flavor from the named flavors. but they are made to come last
always. where is l1ie illli('rilallcc-orci('r alld \'llllilla~tla\'(}r insertioll alld tlJis ('xplain('d?
:flavor - not - instantiable
This flanlr is not itself inswntiahlc. This should he specified for things which are not
complete in thcmsrlves. hut mixill jlavors-flavors which arc meant to be mixed in to
provide some aspel.:l of other flavors.
:init- keyw~rds
AJlowa[~ie keywords which make-instance will pass along to the :init message when a
fbvor is instantiated.
:default-init-plist
Alternating keyword-values. which are supplied to the :init message when a flavor is
instantiated. unless the keyword was supplied already to make-instance.
:documentation
ummmm
defmethod (flQ\lor-name message-name [message-type» arglist body ...
Defines a method m(,ssage-name for flavor. message-type is not supported. do not use it.
arglist is any lambda-list acceptable to NIL. self will be bound (lexically) for the
evaluation of body.
Lexical instance variables are correctly enclosed by the NIL interpreter in this version of
NIL. The only time this can fail is if there is any funny stuff with how the definition is
being perfonned, like evaluating a defmethod inside the lexical environment of another
defmethod or a defun. This would not work compiled anyway.
defmethod-primi t iva (flavor-name message-name) arglist body ...
lbis is used to define a method without interfacing to deal with the self variable or the
instance variables. 111e arguments which the generated function receives wi11 be the object,
the map vector, the message, and the other arguments. This routine exists primarily for
primitive low-level method-generation code, as that which might be used by defstruct.
MC:NILMAN:FI.AYOR 44
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System-Defined Messages 176 Nn~ Manwll
18.2 System" Defined Messages
Here are. some of the messages the system uses to deal with objects defined by defftavor. and
what they mean. .
:print-self strtam level slashifrp
The object should print itself to the stream sitcam. level is the recursion level of printing.
and should be compared against the dynamic value of prinlevel. slashify·p being non-null
mC.tnS that thc output should maybe be re-readable: it is bcing done by prinl rather than
prine.
If you use this in a non-trivial fashion (specifically. if the object will he printed in a nonatomic
fllshion). then it might be re'lsomlble to define methods fhr the pretty-printcr using
thc :pp-dispatch and :pp-anaphor-dispatch methods. ,md define the non-pretty-printing
:print-self method in tenns of how the pretty-printing is perfonned. This is described in
[7].
: equa 1 uthe,...object
The method should return t if its object is equal to olher"()~iec(. nil if it is not. olhe,...
object will be of the ex(\ct same type as the object receiving the mess~1ge (a consequence
of the fonnal definition of equal. page 20). This message is also used by eqf (page 20)
on numerical types which arc not "primitive" NIL data types.
:sxhash
The object should return a hash encoding of itself. such that two objects which are equal
have the same hash. See the description of sxhash. page 119, for the semantics which
must be enforced, and note also the default :sxhash method. page 177.
:8val
AJIows extending the evaluator in strange and wondrous ways to handle evaluation of nonlist
fOnTIs. Note that certain types which arc defined· to self-evaluate do so by spccial case
checks in the interpreter, so one cannot change the evaluation behaviour of those types.
The compiler can't handle these extensions however.
: funcal1 argument-vector
This is what happens by default when a funcal. is performed on an instance. argumentvector
is a stack vector (section 3.1, page 15) of the arguments.
: describe ?arguments?
This is what is used by the describe function (page 222).
:exh1b1t-self stream
:select-nth n
: store-nth n value
These are used by the exhibit function (page 222) to define how exhibition is perfonned
on objects of the given type. lbsically. exhibition is initiated by sending the objccta
:exhibit-self message; it should respond by printing out the appropriatc infonnation. and
returning the nUlnbcr of "slots" Of "indiccs" which it includes. (Try exhibiting various
l'IL objects to see the fonnat: do not include ule clear-screen in the display. The indices
MC:NII.MAN;FLA VOR 44
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iiutitT
W
Nil. Manual 177 Message I )efaults
printed out in the initial display are printed by this method.} Then. the ohject will be
sent (as the llserinteracts) :select-nth and :store-nth messages to select' and store the
corresponding components. GeneraHy.there is no need to define such a method for
ordinary flavors. as the method inherited from vanilla-flavor will show the instance
variable names etc.
: pp-d1 spatch lonnat-description?
:pp-anaphor-d1spatch
These are used hy the !,:1I. pretty-printer [7]. :pp-dispatch is used to control formatting:
to use this you will need to eonsult the pretty-primer documentation. :pp-anaphordispatch
is used lO detect circularities in the structure heing printed: all that is nOlmally
needed is to call the fUI1l:tion pp-anaphor-dispatch on each of the components which
will he printed by the :pp-dispatch method. These methods should be defined in pairs.
so that they refer to the same set of components.
18.3 Message Defaults
Here are some of the messages provided by vanilla-flavor. and what they do.
: p r i n t - se 1 f stream level 'slashify-p
Prints something vaguely infonnative.
: get-handl er-for messa~e-name
Returns the handler function for the message message-name. or nil. In NIl.. this is.
necessarily of type compiled-function.
: operat 1 on-handled-p message-flame
Returns a non-nun value if the object supports a message message-name, nil otherwise.
:send-if-handles message &rest args
If the objcct supports message t then it is sent that message with arguments of whatever
args were passed; otherwise, nil is returned.
:wh1ch-operations
A list of aU of the messages which the object handles is returned.
dynamically and cached on a per-flavor basis.
This is computed
:equal
By default, two objects are equal only if they are eq. If the object has interesting
criterial components, it must define an equal message to compare them.
:sxhash
The default :sxhash simply returns a hash computation on the name of the flavor. The
reason for thi!\ is that if two objects are equal. their sxhashes must be equal. So, if the
object docs anything interesting for the :equal message. it should probably define a
compatible :sxhash message so that different objects will hash differently,
MC:NII.MAN:FLA VOR 44
23-DEC-83
- . ,
- ~~ ~ -' - ... - - - - '
, '
~ "4' ~ •
~: ~. ' , ,-' ..:, ," ; _..', " .
- ", -. ,- . . '

Message J}efaults
:8xh1b1t-self stream
:s818ct-nth 11
: store-nth 11 value
178
Nfl. Manual
'Ibe default exhibition method displays the all of the instance vari,lbles of the instance.
and their values. The selcct and store methods just allow onc to felCh and modify the
variables by index.
: pp-d1 spatch jOnllat-dcscripliol1?
The defillilt :Pp-dispatch method "reily-prints the object the way it "rint~ (vi,1 :printself).
,lIld treat~ il as iIIomic. If you define a :print-self method for something. the :pp_
dispatch method ma} n(n fimction 'I~ desired. in Illal it will nnl dn any "mnallil1g nf the
components.
:pp-anaphor-d1spatch
The default :pp-anaphor-dispatch method dnes nothing. nn the grounds that the :pp_
dispatch method will not be· printing any comp{)ncnt~.
MC:NILMAN:FLAVOR 44

NIL Manual 179 Input, Output. and Streams
19. Input, Output, and Streams
Input and output in NIL is pcrfonncd by operations on streams. Some streams can operate in
only onc direction (input or output), and some can operate in both.
str8amp x
Returns t if x is a stream. nil otherwise.
Most operations on streams are perfonned by functions which take the stream as one of its
arguments. possihly defaulted. Although ultimatc1y the stream operations turn into messagepassing
using the flavor system. these thnctions arc the pertcrrcd way to do things. as they
pert(lnll what mediation might be necessary between the desired eflect and the stream's
~apabi1ities.
19.1 Standard Streams
The folJowing variables have as their \'ah1es streams used for variolls purposes. In the future,
the names will b\.' changed to have • characters at both ends; e.g.. standard - input wi11 become
·standard- input •.
standard-1 nput
Variable
This is used as the default stream for various input functions. and for the toplevel and
breaklevel loops.
standard-output
Variable
This is used as the default stream for various output functions. and for the top level and
breaklevel loops.
terminal-io
Variable
The value of terminal-io is ordinarily the stream which connects to the user's console.
error-output
Variable
This is the stream to which error messages should be sent Nonnally, it directs output
through the value of terminal-io (but see comments below), but it could be made to
send them to a file. for instance. (This may not be used properly yet.)
query-10
Vanabk
This stream is used to ask questions of the user. Normal1y it uses the tenninal, but could
be made to (for instance) log both the input and the output of the transactions .
• trace-output.
Variable
This is the stream to which output from tracing (see the trace function. page 220) is sent
All of the above streams. with the exception of terminal -io. are initially bound to synonym
streams which pass all operations on to the stream which is the value of terminal-io.
MC:NILMAN;NEWIO 27
23-DEC-83
.. ' '. . ... ". .... :;'::/:. .
. '. .' . ..'
.
. '.. . ..
_ ~ " • - , c'. :_::- . " ' _. ' _ ' . _ _ ,- "'. "

Stream Creation and Operations 180 Nil. ManuaJ
The value of terminal-io should not nonn

Slream Creation and Operations ]82 NI14 Manual
make-synonym-stream symbol
This milkes a S)'1I01lYIl1 stream. Such ,t stremn directs (most) operations on it to the
current dynamic binding of the variable symbol. In this way. the stream produced can
always be indirecting to another stream, even when the value of symbol changes by its
being bound Of setqed.
make-str1ng-output-stream &optional &key (:Iine-Iength 79) (:line-number 1)
(:page-fength 60) (:page-number 1) (:character-position 0)
This crc.Hes a stream which wi11 "ccumulate all .output given tn it. This output may be
obtained as a string by get-output-stream-string, be1ow.
The optiolls are used to initi.tlil.e various parameters of the stre4lrn. so thal f

NIL Manual 183 Input Functions
19.3 Input Functions
First some functions not specific to ascII mput streams (necessarily). listen and clear-input
could conceivably be meaningful on strange peripheral. devices (dreamer, aren't i?).
listen &optional input-stream
lllis will return nil jf there is no input immediately available from input-sream. non~null
otherwise. On a terminal. the intent is that it tells whether the user has typed some input
which has not been read yet. On non-interactive streams it should be true except at endof-file:
most streams probably don't SUppOft it yet.
clear-input &oplional input-strcam
Flushes bufiered input from input-stream. This only works on the terminal right now. (It
isn '( really meaningful for non-interactive streams.)
19.3.1 Ascii Input
Most of the functions which read input t(ike arguments input-strcam and eofmlue. In general.
if input-stream is nil Of not supplied. it defaults to the value of standard-input: if it is the atom
1. the value of terminal-io will be used.
If no eofvalue is specified. then an error will be signalled at end-of-file. otherwise the eof
value will be returned. Specifying an eofvalue of nil is 110/ equivalent to specifying no eofvalue,
When input is read from an interactive stream, the characters typed will be echoed at the
user. For those functions which do some significant amount of reading. such as readline or read.
rubout processing will be provided. In this case. specifying an eofvalue means that if the user
auempts to ttruh oul" past the beginning of what he was typing, the function will return ('of
value. instead of requiring him to type a complete expression (line, s-expression, whatever the
function calls for).
What actually happens right now is that specifying an eofvalue when reading from an
interactive stream, dies.
read-char &optionaJ input-stream eofvalue
Reads one character from input-stream.
This doesn't seem to take eofvalue yet?
peek-char &optional input-stream eofvalue
Ibis definition is wrong. The arguments should be peek-type. illput-slream, eofvalue. It
will eventually be fixed.
Peck- at a character in the input stream. Like read-char. but the next call to read-char
will return the same character.
MC:NILMAN:NEWIO 27
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---------------------------------------~====::::.::==--......
5.7.7 •
.,r.~.r.?..-r.. 1I1I1I1I
Output Functions 184 NIL Manual
unread-char character &optional input-stream
Undoes a read -char. peek -char. in the simple case, could have been (sometimes. is)
defined as being a read-char followed by an unread-char of the character just read.
Input streams are only required to support the ability to baclC up one character:
unread -chars without intervening read -chars are an error.
multiple
re8dl1 n8 &optional input-stream eofvalue
Reads a 1ine of text from input-stream and returns it. as a string.
returned. which is t if end-of-file was reached. nil otherwise.
A second value is
read &optional iI/put-stream ('ofvalu('
Reads one s-expression from inpul-slream. and returns it.
discllssed in section 16.3. page 126.
Reading and reader syntax is
19.3.2 Ilinary Input
The semantics of binary input arc stream specific. In general. integers of some significance
are read. and Nil. places no special interpretation on any particular values. The only sort of
binary input NIL supports. however. only reads unsigned eight-bit bytes from disk files.
read-byte input-stream &optional eofvalue
Reads one byte from input-strt'(lm and returns it as an integer. unless end of file is
reached. in which case the nonnal end-of-file behaviour occurs.
19.4 Output Functions
Similar to the input functions. if an optional output-stream argument is not supplied to an
output function. it defaults to the value of standard-output.
First some functions applicable to both ascii and binary streams.
force-output oU/put-stream
The purpose of force-output is to ensure that no output which may have been produced
is sitting around in anyone's buffers. If output-stream is buffered by NIL. the output
should be sent to the operating system (or whatever). and if necessary, the operating
system told to send the contents of its buffers off to their eventual destination.
In practice this doesn't do anything yet in NIL.
f1 n 1 sh-output output-stream
This is like force-output. and additionally docs not return until the output has actually
reached its destination.
If a stream docs not handle this. which no currently implemented NIL streams do, a
force-output is done. q.v.
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NIL ManU4l1 185 Output Functions
c188r-output oU/pllI-stream
The Pllll10se of this is to cause as lillIe as possible of any output already sent to ou/pu/­
s/reall1 to reach its destination: just as force-output attempts to get al1 buffers sent off,
clear-output attempts to get all buffers flushed.
"Ibis is primarily intended for tenninals. although it could be meaningful for random
other devices (ascii and binary). It does not do anything. and is not really expected to.
to a random disk file.
It doesn't do anything to anything in NIL
19.4.1 Ascii Output
write-char char &optional output-stream
Writes char to (}utpu/-slream.
terpr 1 &optional OUlpul-s/ream
fresh-line &optionaJ Oli/pul-stream
terpri perfonns a newline on oUlpu/ .. stream.
fresh -line does so. unless it can detennine that the "cursor" is at the left margin.
fresh-line is supposed to return t if it perfonned a newline. nil otherwise. terpri always
returns nil. fllr historical reasons.
ous tr strillg &optional oUlpul-stream (start 0) COUllt
Standard !':Il. string-output. Outputs the characters of string, starting at index slart and
proceeding for count characters, to oUlpu/-stream. This is not defined by CO!\1MOi' lISt>.
but has been in NIL for some time and is extremely useful for doing efficient output
because it passes a pseudo-substring defined by start and· count along· to the stream. Most
NIL streams do this more efficiently than single-character output, especially the· terminal
stream.
wr 1 t8-str 1 ng sIring &optional stream
wr 1 te -11 n e string &optional stream
Writes the characters of string to stream. write-line fol1ows them by a newline (terpri,
page 185). In NIL this is almost always faster than using a loop of write-chars.
pr1 nc object &optional output-stream
pri n1 object &optional output-stream
pr 1 nt object &optional output-stream
Standard Maclisp-style printing functions.
prin1 is the basic printing function, which attempts to output the printed representation of
object to output-stream in such a way that it might be reconstructable with read. No
. newline or \\hitespace of any kind is output before or after, so delimiters of some sort
might be needed between successive calls.
MC:NILMAN:NEWIO 27
23-DEC-83
. . .,.. ..... ",- -
..... ~. -./"- : ~~ - ~.. -
. .•. . ... ... . ..~... .•.... ~:. ;~~' ~ r:~:';; ~;:; ~~i;.··~ ,..~ ~~,~ ~,~~:~~ '-..;:;.:!C:,C;:?1::.,'.: .' / . .:. .

• 0>' , • .';,', ,-~.,
• :,' ~
~'
:. :~.~-~::; .". ',':, '-:~ '.

NIL Manual 187 Fonnat
In r\1I .• pretty-prinl attempts to detennine the existence of circular structure. and show
this somehow without blowing up.
The pretty-printer itself is described in much more detail in [7].
pretty .. pr1 nt ()~iccl &optional stream
pretty-prinl. with a terpri first and output of a space character after. This. pretty-print
is to pretty - prin 1 as print is to prin 1.
oNccl &oplional stream
Like pretty-prinl. but does 1101 assume that ol~irci
pretty~pr1nl-datum
is l.ISP code.
pretty-pr1nt-datum ()l~irct
Similar.
&optional stream
19.6 Format
This section is a quick reworking of the chapter on format which appeared m [3]. It omits
topics specific to implementations of format other than Nil's. and includes references to
differences between what NIL currently provides. and the definition of format provided by
CO\.1MO!': LISP. It is not known at this time how the COM\40N LISP definition of format wi11 affect
the MACUSP implementation. which utilizes the same source code as the ~J1. implementation right
now. The ~IL version of format will of course be made to confonn to the CO~1MO:--'; LISP
definition.
format destillation cOlztro/·string &rest args
format is used to produce fonnatted output. format outputs the characters of collIro/­
SIring. except that tilde C'-tt) introduces a directive. The character after the tilde.
possibly preceded by arguments and modifiers, specifics what kind of fonnatting is desired.
Some directives use an element of args to create their output.
The output is sent to destination. If destillation is nil. a string is created which contains the
output. If destination is t, the output is sent to the "default output destination", the value of
standard-output (page 179). Otherwise, destination should be an output stream.
?fot'mat destination comro/-string &rest args
This is equivalent to format except that destillation is interpreted just like the stream
argument to print-nil means "the default" (the value of standard-output), and t means
"the tenninal" (the value of terminaf-io). This only ,exists in MACLISP and NIL.
A directive consists of a tilde. optional decimal numeric parameters separated by commas.
optional colon (n;") and atsign ("@") modifiers. and a single character indicating what kind of
directive this is. The alphabetic case of the character is ignored. Examplcs of control strings:
"-S"
This is an S directive with no parameters.
"-3 t 4 :@s" 'This is an S directive with two parameters, 3 and 4,
and both the colon and atsign flags.
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Format 188 NIL Manu~11
format includes some extremely complicated and specialized features. It is not necessary to
understand all or even most of its features to use format cfficiently. The beginner should skip
ovcr anything in thc fo1Jowing documentation that is not immediately useful or clear. The more
sophisticated features are there tilr the convenience of programs with complicatcd fonnatling
requirements.
Sometimes a numcric paramcter is used to specify a character, for instance the padding
character in a right- or left-justifying operation. In this case a single quote (') fol1owed by the
dcsircd ch.tractcr may be used as a numeric argument. Fur example. you can use
"-5. 'Od"
to print a decimal numhcr in five columns with Icading zcros (the first two parameters to -0 arethc
number of columns and the padding character).
In place of a numeric parameter to a dircctive. you C,1Il put the letter v. which takes an
ilrgumcnt from args as a parameter to the directive. Nonnally this should be a number but it
doesn't rea1Jy ha\'c to be. '111is feature al10ws variable column-widths and the like. Also. you can
use thc character # in place of a parameter: it represents the number of arguments remaining to
be processed.
It is possible to have a directive name of more than one character. The name need simply be
enclosed in backslashes (U' tt); for example,
(format t tt-\\now\\" (status daytime»
lbe backslashes above are doubled. because hackslash is the quoting character in COMMON LISP.
Bec:!t!sc of this. t.'1~ fer!.':!rd-sbsh Chaf:lctcr {I} '.'.'iH prob:lbly be mnde synonymou:; with buckslush.
but as of yet it has not been. As always. case is ignored here. There is no way to quote a
backslash in such a construct No multi-character operators come with format.
Once upon a time. various strange and wonderful interpretations were made on c01l1ro/-slring
when it was neither a string nor a symbol. Some of these are still supported for compatibility
with existing code (if any) which uses them; new code. however, should only use a string or
symbol for cOlltro/-string.
19.6.1 The Operators
Here are the operators.
-A arg, any USP object, is printed without slashification (like prine). - nA inserts spaces
on the right. if necessary,' to make the column width at least n.
-millcol.colillc.millpadpadeharA is the rull fonn of -A. which allows aleborate control
of the padding. lbe string is padded on the right with at least millpad copies of
padchar: padding characters are then insened colinc characters at a time until the total
width is at least mincol. The defaults are 0 for minco/ and minpad. 1 for colinc, and
space for padehar. The atsign modifier causes the output to be right-justified in the
field instead of left-justified. (The same algorithm for calculating how many pad
characters to output is used.) The colon modifier causes an arg of nit to be output as
O.
-S This is identica1 to -A except that it uses prinl instead of prine.
MC:Nll_MAN:fORMAT 7
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NIL Manual 189 Format
-0 Decimal output. arg is printed as a decimal integer. -11,111.00 lIses a column width
of II. padding on the left with pad-character III (default of space). using the character
(} (default comma) to separate groups of three digits. These commas are only inserted
if the : modifier is present. Additionally. if the @ modifier is present. then the sign
character will he output unconditionally: nomlally it is only output if the integer is
negative. If arg is not an integer. then it is output (using prine) right-justified in a
field 11 wide. using a pad-character of m. with decimal output radix and trailing
decimal point suppression.
If arg is not an integer. then it is output in the specified field (as hy -A). in
decimal.
-0 Octal output. Just like -0: if a"g is not an integer. it is output (as by -A). in octal.
-8 Similar. but hinary (base 2).
-p If arg is not the integer 1. ,1 lower-case "s" is printed. ("P" is for "plural".) -:P
docs the same tlling. after hacking up an argument (like .. -:.... below): it prints a
lower-case s if tl1e lasl argument' was not 1. -@P prints "y" if tl1e argument is L or
"ies"if it is not. -:@P docs the same thing. hut backs up first.
Example:
(format nil "-0 Kitt-:@P" 3) => "3 Kitties"
-* -* ignores one argo -11* ignores the next n arguments. 11 may be negative. -:*
backs up one arg~ - n:. backs up 11 args.
-1l@. is an "absolute gOlO": it "goes to" the 11th argument.
This directive only affects the "local" args. if control is within something like -{,
-% Outputs a newline. -11% outputs 11 ncwlines. No argument is used.
-& Performs a fresh-fine on the output stream (page 185). -Il& outputs n-1 newlines
after the fresh-line.
-x Outputs a space. -I1X outputs n spaces. No argument is used. This directive is
changing in COMMON USP to mean "hexidecimal output" (done like -0); to get the
effect of the old -X. one can use - T, or some construct utilizing -< or -{,
Outputs a tilde. - n -
outputs II tildes. No argument is used.
-newline
Ti1de immediately followed by a newline ignores the newline and any whitespace at
the beginning of the next line. With a :, the whitespace is left in place. With an @,
the newline is left in place. This directive is typical1y used when a fonnat control
string is too long to fit nicely into one line of the program:
(format the-output-stream "-&This is a reasonably -
long string-%")
which is equivalent to formating the string
"-&This is a reasonably long string-%"
-I Outputs a fonnfeed. -Ill outputs It fonnfccds. No argument is used.
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Fonnat 190 NIL Manual
In the current implementation. -I wiJI do something like try to clear the screen on a
terminal. However. this will be changed: the intent of -I is to output the page
separator character. which might be inconvenient to type in or have sitting in tJle
middle of a fonnat· string in ones source file. To get the old behavior. use
-:I-eventually -I will be changed.
- T Spaces over to a given column. The fun fonn is -destillatiol1,illcremel1tT. which wi11
output sufficient spaces to move the cursor to column destinatioll. I f the cursor is
already past column destination. it will output spaces to move it to column
destilla/ioll + iucrelllellf. k. t(lf the smallest integer value k possible. illcrrmelll det~llIlts
to 1. This is implemented by tJ1C format-tab-to function. pagc IlJ6. On certain
streams. this may not actu'llly Olltput sptlces. but may usc cursor positioning: mus.
one should not depend on -'I' "erasing" text by the typing of spaces.
This will be changed slightly to eliminate a common and unsightly fencepost.
Currently -Twill do nothing if the "cursor" is exactly at column drstillalioll;
however. it will be changed S(l that spacing will be done then too.
In the future. -@T will do relative positioning.
-0 -0 uses one argument. and applies it as a function to params. It could thus be used
to. for example, get a specific printing function interfaced to format without defining
a specific operator for that operation. as in
(format t "-&; The frob -vQ is not known.-%"
~~~~
• • ....,..,
'~~~h_~"~~+~"\
•• Wa.I ,.,•• If "" '- I I
The printing function should obey thc conventions described in section 19.6.2. page·
194. Note mat tJ1C function to -0 follows the arguments it will get, because they are
passed in as format parameters which get collected before the operator's argument.
Not in COMMON I.ISP.
-[ -[SlrO -;5Irl -;•.• -;slrl1-] is a set of alternative control strings. The alternatives (caned
clauses) are separated by -; and the construct is terminated by -]. For example.
"-[Siamese -;Manx -;Persian -;Tortoise-SheU -;Tiger -;Yu-Hsiang -]kitty".
The argth alternative is selected; 0 selects the first. If a numeric parameter is given
(Le. -liD. then the parameter is used instead of an argument (this is useful only if
the parameter is It # It). If arg is out of range no alternative is selected. Aftcr the
selected alternative has bcen processed, the control string continues after the -].
-[SlrO-;slrl -; .•. -;slrn-:;de!au!I-] has a default case. If the lasl -; used to separate
clauses is instead -:;. then the last clause is an "else" clause, which is performed if
no other clause is selected. For example. "-[Siamese -;Manx -;Persian
-;Tortoise-Shell -;Tiger -;Yu-Hsiang -:;Unknown -] kitty".
-[-lagOO,lagOl,... ;slrO-lagIO,•.. ;5Irl... -] allows the clauses to have explicit tags. The
parameters to each -; arc numeric tags for the clause which follows it. That clause is
processed which has a tag matching the argument. If -:al ,a2 ,bl ,b2,... ; is used, then
the fol1owing clause is ~1gged ilOt by single values but by ranges of values al through
a2 (inclusive), bl through b2, ctc. -:; with no parameters may be used at the end
to denote a default clause. For example. n_[";"+,'-,'.,'II;operator -'A,'Z,'a,'z;letter
-'O,'9;digit -:;other -)".
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Nil. Manual 191 Format
-:[jil/sr-;Irur-] selects the ]iI/SC control string if arg is nil. and selects the Ime
control string otherwise.
-@[lfUr-] tests the argument. If it is not nil. then the argument is not used up.
but is the next one to he processed. and the one clause is processed. I f it is nil. then
the argument is used up. and the clause is not proccssed.
(setq prinlevel nil prinlength 5)
(format nil "....@[
PRINlEVEl=-D-]-@[ PRINlENGTH=-D]"
prinlevel pr.inlength)
=> "PRINlENGTH=5"
-R If there is no parameter. thcn arg is printed as a cardinal English nllmh~r. e.g. four.
With the colon modifier, arg is printed as an ordinal number, e.g. fourth. With the
atsign modifier. arg is printed as a Roman numeral. e.g. ) V. \Vith hoth atsign and
colon. arg is printed as an old Roman numeral. c.g. 1111.
I f there is a parameter. tilen it is the radix in which to print the number. The flags
and any remaining parameters arc used as for tile -0 directive. 1ndced, -0 is the
same as -10R. The full fonn here is therefore -radix,millco/,pacichar,co1l1mocharR.
-C arg is coerced t(~ a character code. With no modifiers, -C simply outputs this
character. -@C outputs the character so it can be read in again using the # reader
macro: if there is a named character for it. that will be used, for example
It # \Return": if not. it will be output like "# / Alt. -:C outputs the character in
- justifies le:,.-I within a field millca! widc. lexl
may be divided up into segments with -;-the spacing is evenly divided between the
text segments. \Vith no modifiers. the leftmost text segment is left justified in the
field. and me rightmost text segment right justified: if there is only one. as a special
case, it is right justified. The colon modifier causes spacing to be introduced before
MC:NII.MAN:FORMAT 7
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Fonnat 192 NIL Manual
the first text segment: the atsign modifier callses spacing to he added aner the last.
millfJcld. default D. is the minimum Ilumoer of fJd(leliar (def~llllt space) padding
characters to he output between each segment. I f the to~lI width needed to satisfy
these constraints is greater than minco/. then millco/ is adjusted upwards in co/inc
increments. co/im· defaults to 1. For example.
(format nil "-lO") => "foo bar"
(format nil "-lO:") => " foo bar"
(format nil "-lO:@") => " foo bar"
(format nil "-lO") => " foobar"
(format nil "-lO:@") => " foobar "
(format nil "$-10... ·." 2.59023)
=> "$•••••• 2.59"
If -" is used within a -< construct. then only the clauses which were completely
processed arc used. For example.
(format nil "-15" 'fool
=> " FOO"
(format nil "-15" 'foo 'bar)
=> "FOD BAR"
(format nil "-15" 'faa 'bar 'baz)
=> "FOD BAR SAZ"
If the first clause of a -< is tenninated with -:; instead of -;, then it is used in a
spcd'11 wa:i. All Gf the dau5c5 an: pilJ\:c:i5\:d (suh.i(ct ill -'. uf \.:OUi~C). hut un: fif~i.
one is omitted in performing the spacing and padding. When the padded result has
been detennined. then if it will fil on the current jine of output, it is output. and the
text for the first clause is discarded. If. however. the padded text wi11 not fit on the
current Jine. then the text for the first clause is output before the padded text. The
first clause ought to contain a carriage return. The first clause is always processed,
and so any arguments it refers to wi1l be used; thc decision is whether to usc the
resulting piece of text. not whether to process the first clause. If the -:; has a
numeric parameter n, then the padded text must fit on the current line with n
character positions to spare to avoid outputting the first c1ause's text. For example,
the control string
"-% 0" .. -{-

NIL Manual 193 Fonnat
-{Sfr'" }
This is an iteration constnlct. The argument should be a list which is used as a set
of arguments as ·if for a recursive call to format. The string Sfr is used re.pcatedly as
the control string. Each iteration can absorb as many clements of the list as it likes.
If before any iteration step the list is empty. then the iteration is tenninated. Also. if
a numeric parameter n is given. then there will be almost II repctitions of processing
of sir.
-:{str-} is similar. but the argument should be a Jist of slIblists. At each repetItIon
step one slIbtist is lIsed 415 the set of arguments fbr processing sIr: on the next
repetition a new slIbJist is uscd. whether or not an of the lastsuhlisl had heen
processed.
-@{Slr-} is similar to -{slr-}. but instead of using one argument which is a list.
all the remaining arguments are used as the list of arguments for the iteration.
-:@{Slr-} comhines thc features of -:{sfr-} and -@{sfr-). 1\11 the remaining
arguments are used. and each one must be a list. On each iteration one argument is
used as a list of arguments.
Terminating the repetition construct with -:} instead of -} forces sIr to be processed
at least once even if the initial list of arguments is null (however. it will not override
an explicit numeric parameter of zero).
If sir is null. then an argument is used as sIr. }tmllst be a string. and precedes any
arguments processed by thc iteration. As an example, the following are equivalent:
(apply (function format) (list- stream string args»
(format stream "-1{-:)" string args)
rll1is will usc string as a fonnatting sU'ing. lbe -1 { says it will be processed at most
once. and the -:} says it will be processed at least· once. Therefore it is processed
exactly once, using args as the arguments.
-} Terminates a -f. It is undefined elsewhere.
- A This is an escape construct If there are no more arguments rcmammg to be
processed. then the immediately enclosing -{ or -< construct is terminated. (In the
latter case. the -< formatting is perfonned. but no more clauses are processed before
doing the justification. The _A should appear only at the beginnillg of a -< clause,
because it aborts the entire clause. It may appear anywhere in a -{ construct) If
there is no such enclosing construct. then the entire fonnatting operation is
tcnninated.
If a numeric parameter is given~ then tennination occurs if the parameter is zero.
(Hence _A is the same as- # A.) If two parameters are given. tennination occurs if
they arc equal. If three are given. tennination occurs if the second is between the
other two in ascending order.
If - A is used within a -:{ construct. thcn it merely tcnninates the current iteration
step (because in the standard case it tests for remaining arguments of the current step
only); the next iteration step commences immediately. To tcnninate the entire
MC:NILMAN:FORMAT 7
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Fonnat 194 NIL MC:tnual
iteration process. use -: A
•
-IIG This is the old fonn of -n@.. above. In COMMO~ I.1SI>. -G is a floating-point
fonnat directive derived from I·URTRAN G fonnal. New code should use -@ •.
-F Reserved for fixcd.;field floating-point fonnat.
-E Reserved for exponential floating-point fi)rmat.
-$ This is 1101 yet defilled ill N 1'-
- rdig .ldig jir/d,ptldclwr$ prints arg. a flunum. with exactly rdi/!. digits after the
decimal point. The def4tull for rtit!!, is 2. which is convenient fill" printing "mounts of
money. At least /dip, digits will be printed prel'eding the decimal point: leading zeros
will be printed if there would be fewer thanldig. The default for ldig is L The
number is right justified in a field /irld columns· long. padded out with padehar. The
colon modifier means that the sign character is to be at the beginning of lhe field.
before the padding. rather than just to the left of the number. 'Inc atsign modifier
says thal the sign character should alw~ys be output.
In some implementations. if arg is unreason~lbly large. it will be printed in
-field."padchar@A format: i.e. it will be prine'cd right-justified in the specified field
width. This wi11 not happen in the Maclisp implementation, because the range
provided by Honums is not extremely large.
- \ This is not rcally an operator. If one desires to use a multi-character format operator,
it may oe piaced within baCk siash es, as In -\now\ tor tile now operator. See page
188.
19.6.2 Defining your own
Everything in this section is defined in the MACL1SP and NIL implementations of format only.
det1ne-tormat-op
This may be used in two fonnats:
(defi ne-format-op operator varlist body-forms. .• )
and
(defi ne-format-op operator character)
The operator may be a character. suing. symbol. or fixnum code for a character (in NIL,
it is coerced using the string function. page 112). Whichever, it is canonicalized (into
upper case) and will be interned into the same package which format resides in. For
example. the format operator for tilde could be defined as
(define-format-op \- '\-)
For the first format. the type of operator is detennined by decoding varlis!, which may
have one of the following formats:
(params-var)
An operator of exactly zero arguments; params-var will get bound to the
parameters list
(params-l'ar arg-vary
An operator of exactly one argument; params- var will get bound to the
MC:NILMAN;FORMAT 7
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NIL Manual 195 Fonnat
parameters list. and arg- var to the argument.
(params-var . args-var)
An operator of a variable number of args: paramS-l'ar will get bound to the
parameters list. and args-var to the remaining arguments to format (or to the
recursive -{ arguments). The operator should return as its value some sublist
of args-l'ar, so that format knows how many were used.
A definition for the appropriate function is produced with a bvl derived from the variables
in varUst and a body of body-forms. (The argument ordering in the function produced is
compatible with that on the l.isp Machine. which is arg-l'ar (if any) first, and then
params-var.)
standard-output
Variable
Output from format operators should be sent to the stream which is the value of
standard - output.
format: eo 1 on-f1 a9
Variable
format:ats1gn-flag
Variable
These tell whether or not we have seen a colon or atsign respectively while parsing the
parameters to a format operator. They are only bound in the toplcvel call to format, so
are only really valid when the format operator is first caned: if the operator does more
parameter parsing (like -[ does) their values should be saved if they will be needed.
Tne params are passed in as a iist ThIS iist. however, may be temporary storage only: one
should not allow it to be "passed back" from the call to the fonnat operator without being copied
first Also, it is recommended that fonnat params be referenced with elt, and their length
obtained with length, in order that they may be reimplemcnted as some sort of sequence in' the
future (which will probably be a stack-allocated vector for NIL).
Conceptually, format operates by perfonning output to some stream. In practice, t.his is what
occurs in most implementations; in Mac1isp, there are a few special SF As used by format. This
may not be possible in all implementations, however. To get around this, format has a
mechanism for allowing the output to go to a pseudo-stream, and supplies a set of functions
which will interact with these when they are used.
format-tyo character
tyos character to the format out.put destination. character may be either an object of type
character, or the fixnum code for a character.
format-prine object
princs objecl to the format output destination.
format-pri n1 object
prin 1 s frob to the format output destination.
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Format 196 NIL Manual
format-lcprinc string capitalize?
This outputs sIring. which must be a string or symbol. to the format output destination
in lower-case. 1f capitalize? is not nil, then the first character is converted to upper case
rather than lower.
format-terpri
Docs a terpri to the format output destination.
format-charpos
format-linel
Return the charpos and linel of the format output destination. Since in the MACI.lSP
implementation multiple output destinations may be implicitly in use (via outfiles, for
instance). this attempts to choose a representative one. The tenninal is preferred if it is
involved.
format-fresh-line
This performs the fresh-line operation ~o the default format destination. 'The hair
involved in this is mostly subsumed by the fresh-line function in NIl.
for.nat- tab -to destillation &optional increment
rIbis implements - T to the current format destination (q.v.). In NIL, it wi1l utilize the
:tab-to message if that is supported. Otherwise. if it can determine the "current position"
of the format destination. it will output the proper number of spaces; all else failing, two
~paC'~C\ will hp output.
format-formfeed
Performs a formfeed on the format output destination. In NIL, this will send the'
:formfeed message to the stream if that is supported. the :clear-sereen message if that is
supported, otherwise just output the page separator character. The :formfeed message is
supported by a number of NIL streams, and is designed for just this use.
format-flatc
(format-fl ate IannI lann2 ... fonnn)
The fonns are evaluated in . an environment similar to that used inside of format: the
various format output-performing routines such as format-tyo and format-prine may be
used to "perfonn output". In all but the MULTICS MACLISP implementation, standardoutput
will be a stream which simply counts the characters output-it will only support
the :write- char operation.
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NIL Manual 197 Querying the User
19.7 Querying the User
The following routines are built on the fquery function, which is modeled after that of LISP
~1ACIIl~E LISP. fquery is complicated and subject to change, however, and is not jtself
documented here. Of the following routines, y-or-n-p and yes-or-no-p are defined by
C07\1~10~ LISP: the others are not.
y-or-n-p &optional message stream
This prints message to stream (which defaults to the value of query-io), and then reads a
character from stream. It returns t or nil depending on whether the character signified a
posllIye or negative response: space and rllbollt are accepted in place of y and n.
Because it is so easy to gel a mistaken response fhnn this routine. it should be lIsed for
anticipated questions only.
Because it is used for both input and output, Siream must be bi-directional.
yes-(,.'-no-p &optional message stream .
This is similar to y-or-n-p. but requires a more complete answer. Typeahead to stream
is flushed (with clear-input. page 183), and it feeps. before rcading a complete "yes" or
"no" followed by a new1ine.
format-y-or-n-p jhmuJ/-slrill1!, &rcst jiJnl1al-args
Most the time when y-or-n-p is used, people seem to want to lise a fonnat string with
some arguments. This docs that. Input and Olltput is done to query-ia. Otherwise. it
behaves like y-or-n-p.
format-yes-or-no-p fonnat-string &rcst fomrat-args
Similar.
19.8 Filesystem Interface
The NIL filcsystem interface is designed to allow it to refer to more than one filesystem. The
names of files are not represented as just strings· or lists of components. but are objects of type
pathname. The pathname objects for different filesystems or hosts would be of different types,
and operations on files in the filesystem are perfonned with respect to that type. For instance. we
have under development facilities to allow use of the filesyslems of TOPS-20 and ITS through
CHAOS~ET. At the moment, only the local VMS filcsystem is supponed.
MC:NII MAN:NEWIO 27
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Filcsystelll Interface
198
19.8.1 Pathnames
A pathname has six criterial components.
host
This component always contains an object which describes the filesystem the pailiname
refers to. 1\11 pathnames have such a component: no pathname may be fonned without
such a component. 'l1lUs, pathname interpretation is always performed with respect to
some host.
device
This is nonnal1y a string. naming a device.
directory
1\ string naming a dirC'ctory. or a list of strings. if the directory is structured (that is. if
the pathname is in a subdirectory).
name
/\ string. the "primary" or· "root" name of the file.
type
1\ string. thC' "type" of the file. This is not necessarily as tJle C'x/C'lIsion which wil1 be
used to fonn the host~specific pathname string~ e.g., for a VMS filesystem. a file type of
LIS P corresponds to the C'xtension LS P.
version
Thi~ i~ th(' v('~inn nf tht' pathl1atTl~: H!m~Hy it is an integer.
1\ palhname need not refer to an actual file in a filesystem. nor need all the components
(other than the host) be present. An unspecified component is represented by nil. Such a
component may be supplied by later defaulting operations. Components may also contain certain
keywords which arc interpretedspcciaUy:
:wifd
A "wildcard" component.
: newest
:oldest
These are only applicable to the version component of a pathname. They cause the
reference to the filesystem to refer to the newest or oldest version present Only : newest
is actually supported by the VMS filesystem interface.
:unspecific
I f any component in a pathname has this as its value. then the pathname does not refer
to a specific file in the filesystem~ but rather to the group of files which match the other
components. This is nonnally only used for the type or version components. so that one
may refer to the entire group of files with the same device. directory, and name. This
docsn °t have any use in NIL yet; when ~}L pathnames gain the ability to have arbitrary .
attributes (properties) associated with them, it will be significant.
:implied
I f a path name has this as a componC'nt. it means that the device component is a logical
name which will supply the value for that component l11is is llsed as a pbceholder for
"pathname merging tt • All components other than the host and device components may
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NIL Manual 199 Fi 1csystem 111 terrace
wke on this as their value.
:relative
This can only occur within a structured directory component. It is used in the
representation of VMS rooted directories. For instance, the V\1S pathname
_DBAO: [N I l259 .] parses into a pathname with the string "__ DBAO" as its device
component. and the list (" NI l259" . : re 1 at; ve) as its directory component. NIL
uses this in pathname merging.
:elipsis
This is used in representing things like nil $ d; s k : [n i 1 ... ].
pathname \,,:mlld produce a directory component of ("NI L" .
prohably be flushed in t~lvor of utilizing just :wiJd instead.
Parsing that into a
:elipsis). It will
19.8.1.1 Pathname Functions
pathname thing
thing is coerced into a pathname.
If it is a pathname, it is returned.
If it is a list. then it is assumed to be a \L\CI lSi> namc1ist: interpretation of this, and
MACl.IS}> compatible pathname handling. is discussed in

Filcsystem Interface 200 N II. Manual
Under VMS, this is obtained by translating the logical name SYSSLOGIN.
user-work.1 ngd i r- pathname &oplional host
Returns the user's working direclory, as a pathname:
components will be unspecified.
the name, type, and version
For V\1S.
this is obtained from the RMS default directory string. and the 5YS$O 15K
logical name. Note that the RMS default is copied from the command interpr~ter when
the !"II process is created: temporarily exiting the !\H. and changing the default wiH 110t
change the value of this.
user-scratchd 1 r- pathname &optional host
Returns, as a palhnamc, the directory of the directory which should be used hy programs
for writing "scratch" fiJes.
The local-vms host uses the value of the logical name SYS$SCRATCH if thal exists.
otherwise the user's home directory. If for some reason the device field is absent
SYS$OISK is supplied. Note that the v,.lue of the logical name is copied from the
command interpreter when the 'II is created. Temporarily exiting from the 'II "nd
changing the logical name definition will have no effect.
1 n 1 t - f 11 e - pat h name program-name &optional host
This returns the pathn

NIL Manual 201 FilcsySlclll I ntcrfacc
perfonned, such as pathname parsing.
merge-pathname-defaul ts pathllame &optional defaults de/aul!-Iype defoul!-version
lbis is the main merger. palhname may be anything coercible to apathname. defaults
may be a pathname defaults object. a path name. or a string or symbol (which will be
coerced to a pathname first). de/aull-type and de/aull-version may be whatever is allowable
for types and versions.
If it is necessary. palhname will be, parsed with respect to a host detcnnined from
de/aults. If the directory field of it is missing. then that wiJI be supplied by de/aults.
Therc is somc qucstion as to what shollld happcn if thc dcvicc field of palllllOll1e is
Il1ISSl11g: cllrrcIllI~. it b simpl~ filled in from I.I£:t,'wlls. In the I -isp Machine
implcmcntation of this function. it is supplied as thc dcf;llIlt dcvicc for thc host (perhaps
inconsistcntly. for instance only when parsed from a string?): probably what should
happen is that whethcr the devicc comcs from de/ilulls or not is dctcrmincd by thc host.
so that it would if thc dcvices wcre really structured (with directories in them etc.). and
would not otherwisc (wh.ch in I -isp Machine l.isp appears to he mainly for the sake of
the ITS operating system).
If pal/mOille has a name supplied, then if the type and version of the resuning pathname
are defaultcd from de/aull-type and default-version, as necessary. Otherwise, the name.
type. and version are defaulted from dc/aulls. Thus:
(merge-pathname-defaults
"[nil.vaz]fcc" "zyz$disk:[gzb]zz.1:;p:3" "'f .. ,.. 1 " ,
" ... .,) I J
, => #
(merge-pathname-defaults
"[nil.vas]" "sysSdisk:[gsb]zz.lsp;3" "vasl")
=> # #
In the above, it is worth noting that It =" as a pathname component is used as a
placeholder for an unspecified component, and that a file type of lisp is mapped (by the
VMS pathname code) into an extension of Isp, and vas I to vas. The specifics of the
syntax and file-type/extension mapping are described elsewhere.
The default value of default-version is :newest. The default value of default-type is "lisp";
however, it is highly recommended that this not be depended upon, as it may be changed
to come from defoults.
Here are some of the pathname defaults in use in NIL.
-1 oad-pathname-defau1 ts* Variable
This is used to provide pathname defaults for load, compile-file, and any similar
functions. It is initialized to the user's working directory with name F 00 and type lIS P
(sec user-workingdir-pathname. page 200).
MC:NILMAN:NEWIO 27
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-: "" " ":;;.;.>, .;: ", "'.' , "
'':''~: ". ' .. - . i,~ ",- ';'.~-: "" '--.. '..,,',:' " -- .. - , . "-"

FHt'system Interface . 202 Nil. Manual
*defaul t-pathname-detaults.
Variablf
This provides super-defaults for anything that needs them. such as open. with-open-file,
and parsing a pamname· string out of context. It is initialized to the user's working
directory with name FDD and type LISP (see user-workingdir-pathname. page 200) ..
*scratch-pathname-dataul ts*
Variable
This is used by things which must write out "temporary" files. Things which use this
should not modify it: it should be left to the user to set default pathnames for hosts
(primarily for the sake of the device and directory) to say where such files should be
written. See user-scratchdir-pathname. page 200.
For example. the current '" compile function creates a file named aaafoo.vas. and
supplies the de\icc and directory from *scratch - pathname-defaults*.
19.8.2 Opening Files
Files arc opened with the open function (page ISO). or with-open-fite (page 181). and may
he dosed wilh~lose (rage 181). open hy default assumes that the open is a reference to a file.
so coerces its fit st argument to a pathname. and then creates a Slre~lln to the specified file in the
filesystem. NIL currently employs only two modes of file opening. These are :ascii and :byte
modes.
:asc;j will cause the file to be written as variable-length records. with record-attribute of
carriage-return. The existing disk 1/0 code docs not have the intelligence to deal with records
longer than 512 hytes. however. so is forced to tenllinatc records when that limit is reached. To
compensate. so that spurious newlines do not get inserted into LISP files. recordsexactJy 512 long
arc assumed to not actually be tcnninated. but "continued tt with the next record. when read as
input
:fixnum simply uses fixed-length S12-byte records; this is what vas 1 files use.
fs:close-al'-f1'es
In case you do mess up and lose track of some files, this will close all open files (which
have been really opened as streams, not just kludgey temporary opens). Every known
host object is supposed to keep track of all streams which it has open. in such a way as
to be secure against timing screws, so that this may at least be done.
Doing (exhibit fs:.host-instances*) should give one a handle on the open files, as the
host instances should point to the filcs they have open. fs:*host-instances* is the list of
all known hosts, and is used to (among other things) drive host-name lookup.
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~II. Manual 203 Fiksyslcm Intcrface
19.8.3 Other File Operations
probe-f11 e palhname
If palhname (which is coerced to a pathname with the pathname function) can be opened,
its truename is returned; otherwise. nil is returned. This may be used to see if palhname
exists and is accessible. (If a file protection error occurs, probe-file returns nil, although
that may change. as the intent is to see if the file exists.)
~ote file-length and filepos are missing from NIL
All of the remaining functions in this scction deal with either a strcam. or with a pathname.
ror thc fi.mll cr. thc) perform the operation Oil thc open strcam: f(lr the 1.mcr. on the ilk in the
filcsystcm. which may invohc opcning the file tcmporarily. At present. nonc of thcm work on
streams. A futurc edition of the filesyslem code will contain more code written in IISP. and be
much more versatile in this regard.
For the fut ..:tions which arc dcscribed as rcturning an error description. this is prohahly a
string. but may changc to be a more complicated object in the future. (That objcct should.
howc\cr. h

Filcsys(em Interface 204 NIL Manual
19.8.4 File Matching
all files list-ofpathnames
Rcturns a list of pathnamcs matching all of those in Iist-ofpafhnames. This is done. of
coursc. by appending together the lists of pathnames which match each of the pailinames
in list-ofpalhllames.
By convcntion. this matches over all those components not specificd in each pathname.
V\1S docs not allow matching all devices. howevc('. so the device should be specified. or
will be defaulted from somewhere (where? rms dcfault but it shouldn't be). Newest
\ersinns can be matched also. by lIsing the appropriate patJlname synt~tx. Note that clipsis
spccifkalions in directories. and star spccificati(}n~ in names. all work (ft,rtuittlllsiy.
p('rhap~. hu( Lhey work): e.g .. (aUfUes "[nil...]286*.*:'" returns a list (If pathnamcs of
tJle files with highest version number of· a1lthe files in the 'II. hierarchy with first three
char~lclers of their namc being "286".
mapa 11 files jUllctioll Iist-(~r-pathllC1mes
Calls fUllctiol1 on each pathnamc whkh matches pathnamcs in list-ofpalhllames. 'lois is
esscmi,llIy equivalen( to
(mapc jUl1cliull (a 11 fi 1 as Iisf-o.fpallllloml's»
but calJs junction on each as it is generated rather than consing up the list
In fact. atlfiles is imp1emented in tenns of mapaJlfiles.
mapalffires (and hence allfiles) accept a single symbollstring/pathname in place of a list It is
unclear what should be done about this: it is (currently at least) of no usc to NIL to deal with
multiple specifications at oncc. and in fact· the original aU files function in MULTICS MACLISP did
not· takc a list. but only a single pathname.
There is also no kludgy testing in NIL such that if a namelist is specified it must be a fullyspccified
nameHst (insofar as explicit "*" components arc spccified). Thus using a namclist as a
single pathname will be interpreted as a list of pathnames. potentially resulting (incorrectly) in a
match over all the files on the current device... (That was the reason for the ,k,ludgey check in
MACUSP. you see ... )
19.8.5 Loading Files
load filename &key :verbose :package :set-default-pathname :static :default-pathname
:characters :binary :defaufts :print
:verbose
Boolcan: print out lots of gubbish about loading. Default is value of *Ioadverbose-.
:package
override the package specification (if any) obtained. from the file.
:set -default - pathname
Boolean: set the default palhname of the pathnamc-defaults used (see :defaults
and :defauft-pathname. below). Default is value of *Ioad-set-default-
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I\ II. Manual 205 File~yslell1 Interface
pathname •.
:defaults
Specified pathname-defaults to use in place of the value of .Ioad-pathnamedefaults..
(1bis one isn't in COM:vtO~ LISP. Not clear it should be heavily used,
but i can see it has application.)
:default-pathname
Use this for defaulting. in preference to the pathname-defaults. The defaults are
still set in the defaults specified by :defaults (or its absence).
:characters
:binary
Boolean. :binary t implies that the file is a \'ASI. me: :CII:\R:\C ITkS T implies
that the file is LISP text. By default, the file is examined to detellnine which it is.
And, if no type is specified in filcnamc, first a file with type vast and then a file
with type lisp will be looked for.
:static
Boolean: says to load tile file into the static heap. Default is value of .Ioad - instatic
- area •.
:print
Boolean: if not nil. says that the results of evaluation of fonns in the file are to
be printed. Default is nil, and it probably doesn't work anyway: certainly not for
vasl files.
19.8.6 File Attribute Lists
Not too much detail yet... However. it's necessary to use it.
If. on the first line of a source file the characters ft •••"
appear. then the text from the first "•
• _" to the next is parsed as a file attribute /iSI. (Funnyness with multiple lines? Well, anyway, it
works easily on one line.) This text is logically a list of keyword/value pairs, witiI the values
being either single values or lists of values. The entire construct is made invisible to the
processing language by being placed within its commenting construct
; -.- Mode:Lisp; Package:Compiler; Base:l0; Readtable:NIL -.-
might occur as the first line in a NIL compiler source file. It says that the mode of the file is
lisp (this being for the benefit of text editors), and that the file should be read and processed in
the compHer package, decimal radix, and using the NIL readtable. "Lists" of values are provided
for by separating the individual items by commas, as in
; -.- Mode:Lisp; LSB:ppdef.pretty-print-definition -.-
The parsing of tokens in such a construct is pretty rudimentary and crufty. but essentially things
are symbols except for a series of digits (optionally followed by a decimal point) which is a
decimal integer.
File attributes typicany translate into some special binding environment needed for the
processing of the file (in some context). '(be following arc pre-defined in NIL:
package I'llckagr-namc
The file is processed in the package named package-name.
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Filesystem Interface 206 NIL Manu~tl
readtable readlablC'"'lJamp
The file is read in using the readtable named readtable-name.
naming. is dcscribed in section 16.3. page 126.
Syntax. and readtablc
base radix
Binds both the input and output radices. no matter what those damned variables are
named.
radix radix
For those who are confused by base and will be cvcn moreso when the variable is
namcd .base*.
patch-file y('s·0r-110
If yes"or-Ilo is yes (it shouldn"t be specified otherwise). then a variable pruclaiming the
patch-filc-ness of this file is buund. so th~lt various things can see jt and be clc\cr. like
the helpful function which· warns you about rcdcfining a function dcfined by sumcunc elsc
in anothcr file. (said functiun not existing yet).
Isb moc/u/r-nnme,s),slem-llt.1me
This is defined by Isn [4]. not NIl. (q.v.).
When a file attribute list c is parsed. the attribute names arc kcywords, and the values are
either keywords or intcgers (or lists of keywords or integers).
: f11 e-p 11 st pal/mame
If pnf/mnm(> r:m h(' {\p~n~d~ tf1('n this r~tl!ms a d!s~mbodi~d propt'rty list ~':ith the ft!~
attributcs in the cdr. and the lruename of the file in the car. Otherwise. it returns nil.
This probably should be renamed :file-attribute-list.
fs : proces s .... 1 n -1 oad-env 1 ronment plis! [unct palllllame &rcst args
plis/ should be a parsed file attribute list (with ane\'ell number of clements: the cdr of
what is returned by the :file-plist message). palhname should be the pathname which the
file attributes were obtained from.
The environment which is specified by that attribute list is established. and then. fimct
called with arguments of palhname and whatever args were given.
This is what is used by both load. and the compiler. It enables a stable interface to how
bindings and other environment modifications are obtained from the file attributes.
Examination of the source code (the file [NIL. IO]PATHN. LSP) will show the convention
which is used for defining additional file attributes. It is basically an extension of that defined by
LISP MACI UNE USP.
MC:NII.MAN:NEWIO 27 2] .. DEC .. 83

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NIL Manual 207 Filesystem Interface
19.8.7 Internals for Vl\1S Record Man~lgement Services
l':II. contains some primitive routines and datastructure definitions with which I/O can be
performed entirely from LISP code. In fact. recently a special-purpose stream type was written so
that me editor could do very fast record I/O. This is the local-vms-editor-stream stream,
which is in the source file nil$disk:[nil.io]vlocal.lsp, and can serve as an example of
how some of these things arc used. Some of the other primitives which interface to the filesystem
are also written in I.ISP, but arc hidden from the stream code by a functional interface~ these arc
in the file nil$disk:[nil.vmlisp]vmsfile.lsp.
19.8.7.1 Data Structures
The dlltastructures lIsed for R\fS fab. rab. nam. and xah hlocks arc all just simple bit vectors
of the appropriate si/e. There arc liSP macros and constants defined to deal with them: these
definitions \\ ere generated from the VMS \fD} files. For instance. (si:fac$b_rfm jl~/b) returns the
record-fomwt field of a fah. (setf (si:fab$b_rlm ii/b) si:fab$c_ var) sets it to the code which says
that the record format is variable-length rec{lrds. Generall). fields of type byte and word arc
tCtched/set as fiXIlUIllS. longword and quadword fields arc extracted ilHo (freshl~ conscd) simplebit-vectors
of the appropriate length; the setting operation replaces the bits of the structure (in the
right position) with the bits of the object it is being set to, so the operation is in\'enib1c. See
also the files nil $ dis k : [n i 1 . vm 1 is P ] rms s t r. 1 s p and
nil$disk:[nil.vmlisp]rmssub.ls~
The following routines create these structures:
si:maKe-fab
si:maKe-rab
si:mak,e-nam
s1 :maKe-xab code length
Because xab structures vary, one must specify the xab code and its length. For instance,
(si:make-xab si:xab$c_fhc si:xab$c_fhclen)
creates a xab block used for hacking fi1e header stuff.
Resources are defined for fab, rab, nam, and xab structures:
s1:fab
si:rab
s1:nam
MC:NII.MAN:NEWIO 27

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NIL Manual
s 1 : xab code length
Because xab structures can vary in code and length. they must be supplied to the
resource constructor. The appropriate constants are defined. of course. For instance.
(using-resource (si:xab xabdat si:xab$c_dat si:xab$c_datlen)
. . .)
binds xabdat to a xab structure used for obtaining creation and revision dates.
19.8.7.2 Rl\1S and Related I-Iacking
Thr following flln

;\ II. Manual 209 Terminal 1/0
51 : rm5$truncrab
51: rm5$update rab
51:rm5$wa1t rab
51 : rm5$read rab
51: rms$5pace rab
51: rm5$wr 1 te rab
51: rm5$enter fab
51: rm5$par5e Jab
51: rm5$remove Jab
51: rm5$rename Jabl Jab2
51:rms$5earch Jab
s 1 : rms Ssetdd 1 r lIl'w·dirc('/ory-.\pccijicatioll
Returns. and mayhe updates. the RMS default directory. If ncw-dircctory-spccification is
iii:' ta'ic ~\rs dcf~lilt is nut mGdlfkd: i.lthciWisc. it is SCi to iiCn'-dii t'dUi j -Spn ifiud i(JiJ.
which must be a simple string. This is a fairly direct interface to the SYS$SETDDIR
system service.
If the return status is not normal (the value of si:rms$_normal). it is returned in place of
the string.
51: trnlog logical-name
This performs the trnlog system service on the simple string logical-name. It returns a
simple-string which is the translation, or nil.
19.9 Terminal lID
The current ~IL system contains a terminal stream which is translates general operations into
tenninal-specific display codes. Characters output to it (via the :write-char message or the writechar
function) arc interpreted as either display operations (e.g.. carriage-return moves the cursor
to the next line or wraps to the top of the screen, and clears the line it moves to). or as graphic
characters (causing certain characters which are 1101 graphic on typical ascii tenninals to to be
printed with cenain conventions). Line wraparound is performed also.
The best way in which this can be accessed is with the cursorpos function. which is M.\CL1SP
compatible. In t:1Ct. the behaviour of the cursorposable tty stream emulates the behaviour of
tenninals under the ITS operating system. down to the lenninal-width fencepost bcha\'iour due to
the use of the last column to hold the continuation character. (The "keyword ch~lracter" argument
to cursorpos. as defined by MACLlSP. in fact derives from the second character in the escape
MC:NII.t\1AN:NE\\'IO 27
2.1-{ )1':C-83

Tcrmin4tlilO 210 Nil. Milfludl
sequence used perfonn that cursor operation under ITS. Ah wetl.)
cursorpos &optional arg/ argl org3
cursorpos is a MACLISP compatibility function. but it offers an interface to the display
tenninal code which may be safely and reliably used. Note that the arguments. are
interpreted in rather strange manners... As a general rule. cursorp05 is supposed to
return nil if it was not capable of perfonning that particular operation on the particular
stream involved, totherwise. It is 1101 the case, however. that it may be used on non~
tenninal streams: that is an error.
(cursorpos)
rCl11rn~ the cursor position of terminal-io as a pair. (l'crlictll-posilicm. Iwri=ol1lal-posilion).
Both positions arc measured zero-origined. from the top-left corner of the screen. nil
should h(' returned if the stream docs not hme a generally mo\ahlc cursor.
(cursorpos "pos hpos)
Positions the cursor of the stream terminal-;o at that position. Either vpos or hpos may
be nil. in which case the current value is used.
Otherwise. the first arg to cursorpos should be a symbol (or character object). which
may take an additional argument. The case is irrelevant.
C Clears the screen. The cursor moves to the "home" position (top left corner)~ On
a non-display. this outputs a newline .. so always succeeds.
A Fresh-linc. In this instance. the fresh-line functiun (page ]85) is preferred.
T
Z
ftTop. It The cursor is homed, moved to the topIeft comer.
Home down. Bottom left comer.
L Clear-to-end-of-line. From the current position to the right margin is cleared.
The cursor does not move.
E C}ear~to-end-of-screcn. Current position. to right margin, and all following lines.
are cleared. The cursor does no move.
U
Move Up a line. Wraps around the screen. does not scroll.
o Move Down a line. Wraps around the screen, does not scroll.
F
Move Forward a character position.
S . Move Backward a character position. If at the left margin. effectively does U
then moves to the column to the left of the continuation-character column (i.e.. it
backs up the amount by which the cursor would have moved for a single-position
printing character).
K Erase the character the cursor is over (this would not be the last one typed
nonnal1y. see below:)
X B. then K. Simpleminded way to rubout the last character typed.
Hhpos
Set the horizontal position to hpos.
MC:NII.MAN:NEWIO 27
23;.I)EC-83

NIl. Manual 211 Terminal 110
v "pos
Set the vertical posilion to vpus.
The insert-line operation
\ The delete-line operation
111e insert-char operation
the delete-char operation
Additionally, one may specify a stream to cursorpos by giving that as the last argument.
The atom t as a slream means. as with other printing functions. the terminal (the value
of terminal-io). NOle. howe,,' ... that I/O stream a/so lIses the \·,lllIe of terminal-io. rather
lh~1Il standard - output. Note also that the f'{mn
(cursorpos • t)
is interpreted as requesting the cursor position of terminal -io: to do a home-up. one
must use some alternate fonn like
(cursorpos 'top)
(cursorpos #\t)
(cursorpos 't 't)
This strangeness is also \1:\CLlSP compatible ...
19.9.1 l\'Iodifying the Terminal Characteristics
set-term1 na l-type terminal-name
Resets the tenninal characteristics from the tenncap entry found for terminal-name. See
(not-yet-written) .
s1:determ1ne-and-set-terminal-type
This is the routine called on stanup which either defaults or asks for your tenninal type.
: 1 n 1 t-wi th-termcap tenncap-struct
temlcap-slruC[ is what would be returned by si:make-termcap.
19.9.2 Making More Terminal Streams
As noted elsewhere (page 180), open is what may be used to open tenninal streams in NIL.
The :type keyword specifics that a tenninal stream is requested:
:display-tty
This produces a tcnninal stream just like that NIL starts up with. Additional options fed to
open may be used to parameterize it; these are described below.
:cold-Ioad
This produces a "raw" tty which has no display capahility. It docs perfonn some asciiification
of non-display characters output. but perfonns no functions like line wraparound.
:tty
what docs this do? is it left-over from something?
MC:NII.MAN:NEWIO 27
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Terminal 110 212 Nil. Manmll
Interesting additional open keyword arguments which may be specified when opening a
:dispfay-tty:
:terminal-type tenninal-t),pe-name
The terminal capabilities description is obtained from the tenncap entry for ;ennina!-Iypename.
Since one of these is necessary. you might as weB specify the right one rather
than letting it default (the lookup in the daLlbasc may still be necessary).
:cold-load - stream colcJ.load-strt'am
The first arg to open is ignored. and the innards of cold-load·stream (which must be a tty
stream as created by the :cold-Ioad open-type) is extracted to get to the real terminal.
mt.her than opening a new one. (In the ~Il )oadup process. first the terminal streams are
set to be a cold-load stream. and then later they arc reset to he real display-tty streams
using this. This is less important now than it used to he. but still COIneS in handy on
occasion. It's not clear what lise it might be to users.)
19.9.3 Display TTY 1\1essages
In case you want to hack graphics on another terminal Uf something... See also the source
code in nil $ dis k : [ nil . i 0 ] cur so r . 1 s p.
: wr1 te-char char
This is what implements write-char to a display tennina!. with all the interpretation of
char described earlier.
: oustr slril1g slar! count
Note start and COUIlI are not· optional. Using this results in a significant efficiency gain
over individual :write-char messages. because the stream attempts to pass along as many
block-mode operations as possible to VMS.
:wr1 te- raw~char char
This is not actually provided by si:dispiay-cursorpos-mixin. but is required to be
supported by flavors which mix that in. It is how s;:display-cursorpos-mixin expects to
get raw codes out to the tenninal. Obviously. then. if you also wish to get raw ·codcs to
the tenninaI, you may use this message on display tty streams.
: raw-oustr SIring start count
Analogous.
MC:NlI.MAN;NEWIO 27
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NIl. Manual 213 Syntax
20. Syntax
20.1 What the Reader Tolerates
I wil1 defer delli1ed discussion of reader input and printed representation to the forthcoming
("0\1\10:\ I.ISP manual [1]. The LISP MACIlI~F LISP manual [12] also contains a good discussion
of this. What will be presented here is basically a summary of what the current ~IL reader
accepts. lItilizing ("0\1\10~ !.lSI> syntax.
Basically. the IISP reader reads characters from a stream and fonns tokens out of them.
Cert~lin characters cause additional actions to take place: fl)r instance. the ( character \\ iII calise
mulliple (hut possibly zero) exprcssions up to a matching ) to be formed into a list. Some
characters are significant only when they are the first non-whitespace character: the # dispatch
macro character behaves like this: # 0403 is the integer 259 (# 0 meaning "read in octal"). but
foo#o403 is the symbol whose name is the string "FOOH0403". Aside from these, the basic
nile is that if a number can be formed from the characters of the token. it is: otherwise. it is a
symbol. The sole exception is that the period character (.) is wken as a COilS £101. If a character
i~ preceded h) a hackslash (\), then all spccial sig.nificance is rcmo\cd from it. induding ca~e
translation. and it is treated as a token constituent.
Thus:
foobar
foo\bar
259.259
259\.259
IFooBarl
IFoo\IBar\\1
Similarly, the symbol whose print name is Foo 1 Bar\.
259
259.
-259
+259
25\9
\259
1259 1
the atomic symbol FOOBAR
The atomic symbol whose print name is FOObAR
A floating point number. (Currently this is a double-float. But see the later
discussion on floating-point syntax. section 2.1.2, page 4.)
The atomic symbol with print name 259.259.
Vertical bars read a symbol with an characters (except for vertical bar and
backslash) interpreted as constituent characters. So, this is the symbol whose
print name is FooBar. Backslash may be used to include vertical bars and
backslashes in the symbol.
The decimal integer 259.
The decima1 integer 259. A trailing decimal point explicitly forces decimal
notation, not floating-point.
The negative decimal integer - 259.
The decimal integer 259.
The symbol 259.
The symbol 259.
The symbol 259.
MC:NII.MAN:SYNTAX 34
23-DFC-83

What the Reader Tolerates . 214 NIL Manual
1.0d-5 One times ten to the minus fifth power, as a double-float. Sec section 2.1.2.
page 4.
:foo
A colon in a token uses the characters on the left to name the package the
following symbol is to be read into. The "nu1l't package name means the
package into which keywords are read.
s;:foo The symbol FOO. read into the package named S I (the system-internals
package),
si:IFoo\IBar\\1
The symhol Foc ISar\. read into the SI package.
foo#0403
The symbol FOON0403.
I f the token consists entirely of . chamcters (and none h,I\'e been slashified). then it is illegal
unless there is exactly one: that is a COIlS dOl. which is only legal in list/cons fonnation. 'Ibus .
.100. is the symbol whose print name is . FOC •• but ... is an error.
The primitive syntax for a cons is
«('ar . cJr)
In this notation. a list of items a. b. and c would be written as
(a . (b • (c . nil)})
/.isl sYlllax allows us to "elide" a cons dot with a following cons; the dot is eliminated. as are -
the parentheses of the fol1owing cons:
{n h . (r. . nil)
(a be . nil)
and finally. because nil is the same as 0,
(a b c)
llle following characters tcnninate token formation.
cncountered:
( Starts a list or cons. as described above.
and do something special when
) Terminates a list or cons, or some other construct which "matches" with parentheses. such
as #(.
"
Vertical bar terminates token formation.
String syntax. The characters up to the matchine It form the string; .. and \ may be
included by prcceding them with \.
Reads the following expression, and "wraps" it with the function quote. Thus. 'foo· reads
as (quote foo).
ttBackquotc". This is used for constructing expressions. Backquote is described later
(section 20.1.1, page 216). and also in . [3].
Comma is used for performing substitution within backquoted expressions (q.v.).
lbe # character is a diJpauh macro characler. It reads (optional) digits as a numeric decimal
argument, and then dispatches off of the following character. The following arc defined:
MC:NII.MAN:SYNTAX 34
23-Dr:C-S3

JIm 770ns ·rss.rm
NIL Manual 215 What the Re .. ,ucr Tolerates
# I expression
Wraps expression with function. similar to '. Thus. # 'car reads as (function car).
#(xl x2 ... xn)
Reads as a simple general vector 11 elements long (11 may be zero). with those clements.
# * bits
Reads in as a simple bit vector whose elements arc bits (the digits 0 or 1). Thus. #.100
is a simple-bit-vector of length 3: its clement 0 is 1, and its clements numbered 1 and 2
arc both o.
# Bmliol1al
Reads rational. the syntax for a rational number (which. remember. 111

What the Reader Tolerates 216 NIL Manual
# ,expressioll
I.oad-time evaluation. If the expression is being reild nonnalIy into r-.;IL, this behaves like
# " However. if it is in a file being compiled. the compiler will arrange to have
expression evaluated at load (Le., vasload) time. when the containing expression is being
constructed. This does not work yet in NIL.
20.1.1 Backquote
The bockquo/c t:1cility is used filr constructing list structure from a template. Typically. most
of the temp)ate is constant. and the most common use is when what is being cre~ltcd is I.lSf> code.
insid~ of macro ddinilioll!\. In the simplest casco the backquote character (') is used instead of
qllote ('). and. where suhstitution inside the template is desired. a fbnn to be evaluated is
preceded hy a comma character. For instance.
(defmacro push (item place)
t(setf ,place (cons ,item ,place»)
This definition reads in as code which is functionally equivalcnt to
(defmacro push (item place)
(list 'setf place (list 'cons item place)})
Simple suhstilUlion is r. 'len llot cnough. If the commil in a backquotcd expression is immediatcly
followed by an atsigr: charactcr (@), then. instead of simple substitution. the item being
substituted is "spliced" into the containing list:
'(foo .@bar mumble)
(cons ~foo (append bar '(mumble)'»
For instance. the macro
(defmacro always-returning-nil (&body body)
'(progn ~@body nil»
produces expansions
(always-returning-nil)
==> (progn nil)
(always-returning-nil (do-this»
==> (progn (do-this) nil)
(always-returning-nil (do-this) (do-that»
==> (progn (do-this) (do-that) nil)
The splicing is non-destructive on the expression being substituted, as if the splicing happens by
use of append.
In NIL (but not COMMON USP), a comma immediately followed by a dot instead of an atsign
is treated similarly, except that NIL is free to use dcslructive operations for the splicing; that is.
the splicing IS perfonned as if by ncone (page 58) rather than append.
Backquoted expressions may be nested. They should be assumed to be expanded from the
inside out. Consider the following macro definition:
(defmacro defhack (name fn &aux (place-var (gentemp))}
'(defmacro ,name (,place-var)
'(setf .,place-var (,',fn "place-var»»
In this example. the expansion of the outer backquotc expression causes the values of name, tn.
andplace-var to be substituted in; this essentially means that we get (using italics now to show
MC:NJI.MAN:SYNTAX 34
23-DEC-83

.",7- 33 PC - 'sr' ;; 'm' um
NIL Manual 217 The l.isp Reader
the suhstitutions)
(defmacro Ilallle (place-var)
t (set f ,place-var ( • 'fn ,place-var))
Now. ",111" means that we substitute in the value of '''In''. which is of course just /n. which is
what we want: on the other hand, we do want the value of place-var to be substituted in here.
so it does not need that quote.
To see another way that this works. one can manually pseudo-expand 111e illner backquote in
the original defhack definition
(defmacro defhack (name fn &aux (place-var (gentemp»)
'(defmacro .name (.place-var)
(list 'setf place-var (list' .fn place-var»»
which indeed produces what we want. Generally. then. one uses ".." when one wants the
substituted fonn to itself he evaluated and suhstituted with the expansion of the inner hackquote
expression. and ":." when one wants to suhstitute in something which is "constant" with respect
to the inner backquote eXf,:msion.
As one final extension to hackquote. ;\11 allows its use with general vector syntax. This will
prohably he supported fore\'\,~r and evcr. if for no other reason than the 'II compilcr/codegeneralor
emits inslructions as \ectors and conslructs them that way.
'H(foo ,(+ 3 7) bar) => H(foo 10 bar)
"Splicing" syntax (".

The Lisp Reader 218
NIL Manual
;;-.-Mode:Lisp;Readtable:Ml-.-
;; This code uses »:" and "I" as in maclisp.
;;-.-Mode:lisp;Readtable:LM-.-
:; This code reads using the old lispmachine syntax.
C -.-Mode:Fortran;Readtable:Fortran-.-
C This would work if one defined a readtable for Fortran.
% -.-Mode:Lisp:Readtable:Cgol-.-
This is lisp codetn cgol syntax. Yow! % .
define fib(x); if x

Nil. Manual 219 The l.isp Reader
s1 :enter-readtab1e "omr a-readlab/r
Enters a-rrad/ablr giving the syntax for "allle.
specification in the mode-line of a source-file.
name may then appear as a readtablc
create-readtable
Returns a naked read table. with syntax for reading whitepace-deJimited symbols.
s1:add-number-syntax
Adds syntax for parsing numbers to th~ current readtable.
s 1 : add -11 s t - syn tax &optional (opell # \() (closr # \)
Adds syntax ftH' parsing lists to the current readwble.
s1: add-pacKage-syntax &optional (eltar #\:)
Adds syntax for specifing packages to the current readtable.
s1:add-escape-char-syntax char
tv-takes clUJr the syntax-esc,lpe-character in the current readtable.
s1: add-pref1x-op-macro cliar operaTor
Makes char a read macro that returns a list of operator and the next thing read.
example.
(si:add-prefix-op-macro NI' 'quote)
For
20.2.4 Alternative Syntax
The eGOL syntax [11] is available by loading the file NIL$OISK: [NIL. LISPIO]CGOL. LOO.
Further documentation is in the file NIL$OISK: [NIL .MANUAL]CGOL. TXT. The imp1cmcntors
do not recommend the extensive use of CGOL or any ALGOL-Jike syntax for LISP programming,
especially in environments where program readability and editability arc important long range
considerations. However, some feel that syntactic variety taken in moderation is good for the
soul.
egolread
Rcads a CGOL syntax expression.
ego 1 P r i n t expression
Prints an s-expression lisp program in the CGOL syntax.
Another parscr. for a language with syntax compatible with the symbolic algcbra system
MACSYMA [8], is availablc by loading the file NIL$OISK:[NIL.VAS]PARSER. which scts up a
readtable named infix. The readmacro character" #$" has been set up to invoke this parser in
the "NIL" readtablc. One could then writc the following:
(defun f (v a b x)
#$(v[O.O]:COS«A-S).X)/(Z-Z.(A-S)AZ)+COS(V[l.l].X).
v[O.l]:COS«(A+S).X)/(Z-Z*(A+S)ftZ)-V[l.G].V[O.O].
v[l.O]:V[l.l].V[O,O],
v[l,l]:V[O,l]*V[l.O])$)
MC:NII.MAN:SYNTAX 34
23-DEC-83
"".. ~ .
'.' . . '.' ~". .':. ': , . ' •. ~ .. ' c .~~~;. ~ \'; ,;p~j~fi;;~~':\~' ~:;=~. . •... ..... . · . .., .

Ddwgging and Metering
21. Debugging and Metering
220
NIL Manu,!1
21.1 Flow of Control
21.1.1 Tracing
tr ace junction
trace enwraps the definition of junction so that the arguments it is called with. and the
\'alues it returns. may be seen. follc/iol/ is not e\'aluated.
(dafun f (x) (times x x»
=> f
(trace f) => (F)
(untrace f) => (f)
(trace f) => (f)
(f 3) :printout:
#(1 :ENTER F #(3»
#(1 :EXIT F #(9»
The printout is a VECrOR. Its clements are:
{O] Recursion level for the given function
{I] :enter or :exit
[2] Name of the function.
[3J The vector of arguments, or the vector of return values.
Say that you wanted a breakpoint on entry to f. Then say
(defun f-bp (level direction name vector)
(eq direction t:enter»
(trace (f (:break f-bp»)
Presently all trace options work this simple and functional way, the syntax of a trace option is
(:keyword predicate-junction-to-call). or simply :keyword which means the same thing as
(:keyword t). Options are :noprint, :break, and :info.
One exception: (trace (f :menue» enters a simple menue of various kinds of trace options.
MC:NlI.MAN;DFBUG 20
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NIL ~1anual 221 Flow of Contfol
21.1.2 Who docs \Vhat, and Where
who-calls symbol &optional &key (type:/ullction)
This searches all compiled-code modules tp find those which reference the t>pe value-cell
of symbol. type may take on the values :functlon, :value, :Iocal-function. Of :Iocalvalue.
It defaults to :function, thus finding all modules which caB the function symbol.
A type of :value would find, all those modules which referenced symbol as a special
variable. :Iocal-function and :Iocal-value (which should probably be called :Iexicalanyway)
aren't actually useful: they would only find uses where the references were not
compiled away, and all local references are in the current compiler.
Someday this should he smart enough to do searching through all defined functions,
including interpreted ones.
where1 s function
funcTion should be a symbol or a compiled-function. whereis returns the compiled-code
module (the module-object) which d~fines fUlIctiol1. or nil if that cannot he dctennined.
It can only detennine this for compi1ed functions.
Someday (i keep saying that don't i) there will be a more general mechanism, so that the
source file can be detennined for all "defined objects", such as those defined with defvar.
defstruct. defmacro. etc. Until then, note the following function:
51 :module-50urce-f11e module
This returns the name of the source file for the module module. The current
implementation .does this by looking at the vasl file from which module was loaded, so
that file must exist on disk (with the same name).
ap rop05 STring &optional (pkg package)
This searches through pkg and all of its super-packages (see chapter 15, page 121), and
returns a list of all of the symbols which contain strillg as a substring.
51: apropos-generate /n arg &optional (pkgpackage) (superiors I)
'Ibis function maps the function fn over aU symbols which contain arg (a string or
symbol) as a substring, in the package pkg (and its superiors, if superiors is not nil).
si:apropos-generate uses mapatoms (page 122): it is possible that fn could be called on
the same symbol more than once, although that will not happen very often in the current
NIL implementation.
The apropos function is defined using this, by
(defvar *apropos-list*)
(defun apropos (arg &optional (pkg package) (superiors t)}
(let ({*apropos-list* C»~)
(si:apropos-generate
#'(lambda (x) (push x *apropos-list*»
arg pkg superiors}
*apropos-list.)}
One could write \'ariants of this which test the symbol for specific properties. or with
boundp or fboundp, and which print the results as they are computed rather than
MC:NILMAN:DEBUG 20

Examining Objects 222 NIL Manual
accumulating them in a Jist
21.2 Examining Objects
exhibit object
Invokes an interactive structure editor on the object. There is a "7" command to print out
a command menu. The object is scnt any of the following messages. :exhibit-self.
:select-nth. :store-nth. See the defi~jtions K)r built·in objects in
"(N 1I .. SRC]EXH IRI.LSP".
descr 1 be objcct
Says a few things about the object.
21.3 Debug ~lnd Breakpoints
debug
Enters the dehugger. Various commands. self documenting \'ia the "'!" command. Errors
hy defillilt enter the debugger also. Note that in its current SUlte, siAlck and argument
infonnation displayed requires an additional level of interpretation placed upon it for it to
be correct. For example, local variable information currently shows simply the siAlek
between call frames. including argument frames being computed and "dirty" (non-Lisp)
data.
break. tag &optional (predicate-fi,nn I)
break evaluates predicate-!onll, which defaults to t If the result of this evaluation is not
nil. then it enters a "break loop". ":bkpt lag" is printed out. and a recursive read-evalprint
loop is entered. The prompt for reading says ll)break>. where 11 is the number of
nested break loops currently in force. Note that tag is not evaluated.
break is one of the older debugging tools around. It is not nearly as useful as it had
once been, because in a usp with lexically seoped variables, those values are not apparent
from the break loop. In NIL what is probably moreusefu1 would be to insert explicit
calls to (debug) in ones code, rather than to break. )n the future. break win in fact do
that. and its arguments will be a format-string and arguments for the fonnat-string (see
format, page 187).
-break value lag
This is the internal version of break which eva)uatesboth of its arguments nonnally. This
is also how you can give a non-constant tag argument to the break loop. When break is
changed.. this function will go away.
MC:NII.MAN:DEBUG 20
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NIL Manual 223 Metering
21.4 1\tletering
21.4.1 Timing
t 1mer jUnction &optional (loops I) arguments
Calls jUnction with arguments arguments (a list or simple general vector). loops times. and
print" out infonnation on how much time was taken. Try. for example.
(timer #'cons 100 #(a b»
Needs some improvement (() deal with function·cal1ing and loop overhead: for that reason.
this is not too lI~eful with short fast functions.
CO\1\10,\-IISP defines two functions for obtaining compute and elapsed time. Both return
integers in the same units. which can not be assumed to be fixnums. These units arc units of
internal limC'. which cannot be depended on to be the same in different CO\1\10' I.lSP
implementations. They may e\"en differ from one ~IL. release to another.
1 n te rn a 1-t 1 me - un 1 ts - per - second COllS1Lll1t
This is .111 integer v. hich is the numher of "tic~" of internal lime per sl'cond. It h;lprens
that in 'II this is 100. because that is all the accuracy which \\tS pn)\'ides at the
moment. It could change in the future, and its value should not be depended on.
get-1nternal-run-time
This returns the "run time" of the Nil. process in internal-time-units-per-second units.
get-1nternal-real-t1me
This returns a measure of elapsed time in internal-time-units-per-second units. The
time-base for this time measurement may not be depcnded on: only differences between
the values of two successive calls should be used for anything.
runtime
This is the old name for get-internal-run-time. While it is the- same name as the
MACLISP function, it is incompatible-the NIL runtime function returns the run time in
units of hundredths of a second.
elapsed-time
time
elapsed-time returns a measurement of elapsed time. in seconds. as a double·fioat. Two
such quantities may be compared to determine elapsed time. The origin of this number
may not be depended upon: in MACLISP it is the "system uptime"; in ~lL it happens to
be the double·float representation of the number of seconds since thc origin of the
Smithsonian time standard (local time). This quantity is only really accurate to hundredths
of a second. even though it is potentially accurate to IOO-nanosecond tics.
The synonym time is provided for MACTISP compatibility; This name should not be used
in new programs. and should be changed in old programs. as the name time will be
ch~l11ged incomp~ltihly by CO\1:\10~ I.Isr. Also. there is a us» \1ACIII'F I.ISP time
function which returns elapsed time. but as a fixl1um in sixtieths of a second. The
elapsed-time function will continue to exist as the functional equi\alcnt to the MACLISP
MC:NII.MAN:DEBUG 20
23-1 )FC·g3
i
.'. ;-,'
~
~
.. ~
,_:::;,:~~::~~~~:~'o~~',~__ ~:~~: ~: , _- _. . .

Melering 224 Nil. MmlU,d
time function. however.
s1:pagefault-count
This returns the number of pagefaults taken by the process since process creation.
Although this number is interesting to look at to see if the !\:IL is thrashing. it must be
taken with several grains of salt due to the way VMS paging/swapping is perfonned. {The
following discussion should perhaps be somewhere else. under "perfonllallce considerations"?)
The following points arc especially of notc. First this number docs not count the
number of faults taken which involved fctchjng a page from the pagefile (or shared image
file). Rather. it includes those "fault\" for pages which still reside in physical memory,
hut are just not contained within the working set Also. the overhead of doing this
paging is charged to thc process nmtime.
Presumably. then. if one sets the working-set extent (the proccss parameter/user quota
WSEXTENT) high, then the actual working set in use will apprmlch the number of pagcs
of the joh which arc resident in physical n:tcmory. and the count of pagcfaults will bettcr
approximate the number of pagefautts for non-resident pages.
Note also the room function. whichvcrboscJy describes the "irtual memory usage of the !\IL.
including the size of the living heap (Le .. how much consing has been going on).
The ~1A(,usP·compatible status macro provides a gctime option which returns the nmtimc (in
the same unite; as runtime docs) which is the contribution to the proces~ runtime hy the garhagccollector.
This is curr~ntly. of course. alw~lYs zero, When the garhage-c~1ncctor is availahle, there
will be functions which parallel the above threc. which will return the contributions to elapsedtime.
runtime. and pagefaults by the garbage-collector. Note that the values returned by the
above functions will· always include the contributions by the garbage-collector .
. 21.4.2 Function Calling
The only type of function call metering which is available in NIL right now is a global
database of how many function calls (and similar things) of various types have been perfonned
since the NIL was first loaded up.
This number-of-function-calls metering is basically. implemented by the NIL compiler. There
are four tables 10 long: the four tables are for metering
jUnction C'a/ls
Direct function calls. As in (defun f (x) (g x»).
jUncal/s
Simple funcalls.
sends
Calls to send. 'Ibis does not (unfortunately) include lexpr-send.
applies
Cumpiled calls to apply (= lexpr-funcaU).
lbe 10 entries in c,tch table count the number of such occurences for zero through eight. and
nine-or-more arguments. When the compiler compiles (say) a function caU of two arguments, it
MC:NII.MAN:I1EBUG 20
23-DFC;'S3

NIL Manual 225 Metcring
will sneak in an instnJction like
incl w A
cl$call_meter+2(slp)
just before it does the actual function call. This sequence takes four bytes of code.
The intent of this type of metering is to measure how intensively various applications perfonn
function calling. in order that we might· be able to estimate how changes to the function calling
sequence (such as modifications to the function entry code. function call-frame setup code. or
even microcode support for either of those or the function can itself) might affect the performance
of 'II programs. Wc have not yet actually done any measurements with these meters. However.
in the event that they might be useful to' people. the functions (which are somewhat dirty and
kluog.cy) which read them are documented below.
s1:get-cal1-meters
This returns an a-list of the values of the various calling meters. The a-list will be 4 long.
and the first clement of each of these lists is a keyword describing the type of call: the
remaining 10 clements are the numher of "calls" of that type for zero through 8. and
(last) nine or more calls. The keywords are
:function
Direct function calls
:funcall
Compiled calls to funeaU
:send
Compiled caJIs to send
:apply
Compiled calls to apply (Iexpr-funcall).
s i : show-ca l1-meters &optional (merers (si:ger-call-meters)
Prints out the meters.
s 1 : subtract-ca l1-meters after-meters be/ore-meters
Returns a new "meters Hst" in which all of the numbers are the difference of the after
and before values. All of the entries are assumed to be in the same order.
One could get a display of how much function calling (etc.) was going on by doing something
like
(let ({before (si:get-cal1-meters»)
(run-program)
(si:show-call-meters (si:get-cal1-meters) before»
MC:NII.MAN:DFBUG 20
23-DFC-83

__________________'1-...
r~ .... r.r.n ...... ".;.-·.·r.711'17171711'1'17711111)1IIIIIIII
System Management 226 Nfl. Manual
21.5 System l\1anagement
Included are some minimal uti1ity functions for maintalnmg subsystems in ~1L. These tools
are not meant to be a comprehensive set. ttaddressing all the issues" as they say. Instead. they
address some of the issues. have been found' useful. and are used along with individual system
specific procedures for maintaining systems including the editor and MACSYMA.
The practical working procedure on most programs goes something like the following: 'lbcre
are a set of source files that make up the program. One of these files defines a variable set to a
list of these file names. and includes code for loading the files. creating needed package
namespace(s). and peforming other functions as needed. Day-tn-day works procedcs in an
incremental t~lsion. changes are made to the sources using the {-wilt-in editor. and thcse changes
arc testcd and dchugged using editor commands such as CONTROI,-META-C (compile-dcfun. or
-Z) and other lIlilitcs in the system
as needed. The editor. dehugger. evaluator. andexhihitor are invoked many times during a days
dcvelopment cycle. From lime to time during editing t1le changed files arc saved of course. as a
h(l~kup against environment crashes. At the end of ~hc day. (or perhaps. during lunch hour. or
after several days). a recompilalion of the changed program files may he eflected. using some of
the functions documented in this section.
A somewhat paral1el effort is the maintainencc of a system t11at has "users." The same
melhodology as lIsed in a development system is in effect: except tJ1at now the full-rccompilationcycle
time may he months. and there is a definite target-environment which is (0 receive system
ch~!!~g~s in t.~c ferm of "p~tch files." {Sec the d~x:umenc~tion of the put~h fucility.}
Some additional functions documented here provide ways to find out something about how
modules depend on one another.
21.5.1 An example
; This is an example "system-build" file.
(defparameter .my-files.
'("USR:[ME.SYS]TOPLEVEL"
"USR:[ME.SYS]UTILS"
"USR:[ME.SYS]BASIC"»
(defvar .my-modules. (»
(defun load-my-system ()
(setq -my-modules. (mapcar "load .my-files.»)
(de'fun recompi le-roy-fi les()
(mapcar ,'silent-comfile
(mapcan "(lambda (x)
(if (utils:source-need-compile? x)
(list x»)
.my-files.»)
MC:NII.MAN:DFHUG 20
23-DEC-S3

NIL Manual 227
SySl~tn
ManJgcm~nt
{defun silent-comfile (x)
{let «compi1er:*messages-to-terminal? (})
(si:print-gc-messages ())}
(comfile x)}}
(defvar *my-undefined-functions-alist*
( ) )
(defun find-my-undefined-functions ()
{setq *my-undefined-functions-a1ist* ()}
{mape
# ' ( 1 amb d a (m)
(if (typep m 'module)
(uti1s:map-over-modu1e-ce11s
#'(lambda (module symbol key)
(if (and (eq key :funetion)
(not (fboundp symbol»)
(let «a (assq
symbol
*my-undefined-functions-a1ist*»)
{i f a
(unless (memq module (cdr a»
(push module (cdr a»)
(push
(list symbol module)
*my-undefined-functions-alist*»»)
m) ) )
*my-modules*)
*my-undefined-functions-alist*)
21.5.2 "Source (Re)Compilatioo"
ut11s:V8s-source-f11e filename
Gets the exact name of source file from the object file, filename.
ut 11 s: source-need-comp 11 e1 source-filename &optional object-directory
If there is no object file. or if the version of the number of the present source file is
greater than the version number of the source from which the object was compiled then
this function returns t.
ut 11 s: V8S- source-needs - recomp11 81 filename
Gets the source file name for the object filename and checks the version numbers.
MC:NII.MAN:DEBUG 20

Verifk~ltion 228 NIL Manual
21.5.,3 Information in l\1odules
The exhibit function can be used to look at modules interactively.
21.5.4 Related Utilities
These are sometimes used to store information gathered during system programming. for
example. "bug" cases. lists of undefined functions. sorted lists of special variables. ctc.
ut i 1 s : p r i" t - i" to - f 1·1 e rXl'rcsshm &optional filellame
Prints the {'.%prt'ssioll into the .li/('/I

NIL Manual 229 Errors
22. Errors
Errors in NIL work by signalling error conditions using signal. The specifics of this are going
to be changing in various ways: however, the basic interfaces for "creating" errors can hopefully
be kept static, at least insofar as the functions can be made to accept and interpret arguments
upwards-compatibly.
cerror proceedable restartable condition-name lonna/-sIring args
This is what needs to be used to signal correctable errors. For an error to be correctable
(in the current scheme). one uses cerror and gives a non-null proc('cdab1c argument. The
rC.'ilarlah!c arg.ument has lO do with saying that the error can be "restarted" (i.e..
something gets tried over again) by throwing to a 141g with name error-restart: this is
hardly. if ever. used. and will probilbly be obsolete quite soon.
condition-name is the name of the condition being signalled: it is typically. although not
necessarily. a keyword.
fhrl11a1-Sfrillg is a string suitahle as an argument to format with extra arguments of args:
that i~ how the error message is produced. There arc. however. COl1\ entions on what
particular arguments mean for particular conditions: some of them arc described below.
At some point. the error system and how errors (and non-error conditions) arc signalled
will all change. It should be the case, however. that vanilla uses of cerror, especially
cheCK - type place l)'pe-~pecifie,. &optional description
check -type expands into code which verifies that the value of place (which must be a
place suitable for use with setf-see page 38) is of the type type-specificr. If it is not,
then an error is signalled and place is updated to the newly-supplied value. Note that
type-specifier is not evaluated.
description is a string which describes the type; for instance. "an integer", "a prime
number greater than 403". If it is not supplied. then check-type will attempt to
construct such a phrase from type-specifier; however, the current implementation barely
tries at all. so for now it is probably best to specify it.
For example,
(defun oddp (x)
(check-type x gaussian-integer "a guassian integer")
(if (typep x 'complex)
(if (not (logbitp 0 (realpart x»)
(logbitp 0 (imagpart x»
{not (logbitp 0 (imagpart x»»
(logbitp 0 x»)
MC:NII.MAN:ERROR 15
23-DEC-83

Errors 230 Nil. Mclllual
check - arg place predicat(, &optional sIring
check-arg is an oldcr form of check-type. predicate. if it is atomic. is a function of
one argument to be used to test the value of place:
(check-arg x fixnump "a fixnum")
I f it is not atomic. then it is a form to· be evaluated to test to see if the value of place is
acceptable:
(check-arg x (typep x '(signed-byte 8»
"an eight-bit signed byte")
Even if it wcre to try. check-arg would have even m()r~ tfouhlcconstructing a
descriptivc string on its own than check -type. s() it is rccommended that siloing be
supplicd.
For example.
(defun fact (x &ayx Cans 1»
(check-arg x" (typep x '(integ.er 0 .»
"a non-negati~e integer")
(do «i 2 fl+ i») «>= ; x) ans)
(setQ an~ (* i ans}}})
Hcre are somc of the interesting and well-fonned error conditions defined in NIL right now.
and t11e arguments they expect. (Notc that extra arguments may always be given.)
:wrong- type - argument type-name losing-object
This has to be the most common condition uscd in NIL. type-name is the name of the
type of object which was expected. such as number. and los;llg-o~i('ct is the ooject. (The
type-name is not currently used fOf anything. and lots of code just puts a fairly random
symbo1 there.) The value returned is used in place of the value of the wrong type. For
example. a subroutine which arg-checks for fixnum:
(defun si:require-fixnum (x)
(do () «fixnump x) x)
(setq x (cerror t nil :wrong-type-argument
"-.-5 is not a fixnum"
'fixnum x»»
Wrong-type-argumcnt checks are so common that it is better to subroutinize or macroify
them rather than writing out loops. See, for instance. check -arg (page 230).
:unbound-variable variable
variable was not bound. Returning a value uses that as the variable instead..
:undefined- function name
name is not defined as a function.
instead.
Returning a value uses that as the function name
:wrong - number - of -arguments random
This is handled spastically right· now. will probably be superceded by something else. At
least when called from compiled code. returning a value causes that value to be returned
as if from the losing call.
:invalid - form fonn
fonn was not meaningful to eval. The return value is evaluated in place of the bad fonn.
MC:NILMAN:ERROR 15
23-l>EC-S3

NIl. Manual -231- Errors
:io -Iossage t/escril'l ion Jonn
Sort of a catch-all for random I/O errors. description is a string describing the error. and
Jonl1 is the form which produced it; for instance
(delete-file "[fooJbar.baz")
might signal a :io-Iossage error with a descriplion of the string
"%RMS-E-DNF, directory not tound"
and a Jonn like
(delete-file #

En\'ironmelll Enquiries
23. Environnlent Enquiries
. 232
Nil. Mm1U,tJ
23.1 The Host Environment
lisp-implementation-type
This returns a string which is the name of the uSP implementation, In NIl, this string is
"VAX NIL".
lisp-implementat1on-version
This function returns a string which descrihes the \'ersionsof the systems loaded in the
!\1I. In :\11,. this is the S4Ulle as calling (si:system-version -info t) (see pitge 282 for
more details).
maChine-type
This r(,lllms a string which names the type of machine the !':ll. is running on. such as
"DEC VAX-11/7SO".
machine-instance
Relllrn~a
string which is a (supposedly) unique string naming the m,tchine. such as
"MIT-CORWIN". 'Jbis name wjJJ nonnaJly be the same as that used as the "host" name
by the path name code.
host-software-type
'Ibe sofrware type of the machine. In NIl .•
short-site-name
this is always "VMS".
This returns a shon name of the site, for instance "MIT AI Lab", If this was not set up
in the ~II site parameters file. it win default to what is returned by tJle machineinstance
function.
long-site-name
This returns a long name for the site. such as "MIT Artificial Intelligence Laboratory",
If this was not set up in the NIL site parameters file, it will default to me shon site name
(above). or the machine instance.
23.2 Maclisp-CompatibJe Status Enquiries
(status date)
returns a list of the year (modulo 100), month. and day of the month.
(status daytime)
returns a Jist of the current hour, minute, and second.
(status dow)
returns a symbol which is the fun name of the current day of the week (in English,
sorry), lbe package the symbol is inlCrned in is probably system-internals: perhaps it
should be the keyword package, or the value should be a string anyway.
MC:NII.MAN;ENV 37
23-DEC-83

NIL Manual 233 Privileges
(status gctime)
Returns the runtime contribution of the garbage-collector. This is. of course, alwilYs 0 in
the current NIL.
The first four of these may all be obtained by use of the functions in section 23.5. page 234.
23.3 Privileges
get-privileges
This returns a list of keywords naming the privileges the ~IL
keywords are listed below.
currently has enabled. The
set-privileges &rest kC)'lt'ortis-and-l'o/U(,S
This takes as arguments alternating privilege keywords and flags: if the flag is nil, the
corresponding privilege is disabled. otherwise it is enabled (if that is possible). setprivileges
returns a list of the privileges which were enabled when it finished, just as
get - privileges docs. For instance.
(set-privileges :sysprv t :bypass nil)
(attempts to) turn on the sysprv privilcgc, (lnd turn offthc bypass privilcge.
The privilege keywords defined are
:cmkrnl
:cmexec
:sysnam
:grpnam
:allspool
:detach
:diagnose
:Iog_io
:group
:acnt
Note that for this privilege, the name used in VMS is noacnt; however, NIL uses acnt
because that is the name used by DeL.
:prmceb
:prmmbx
:pswapm
:altpri
The internal name for this is setpri, however OCL uses altpri, so NIL does also.
:setprv
:tmpmbx
:worfd
:mount
:oper
:exquota
:netmbx
:volpro
:phy_io
MC:NII.MAN:ENV 37
23-DEC-8J

Memory Usage
234 NIL Manual
:bugchk
:prmgbl
:sysgbl
:pfnmap
:shmem
:sysprv
:bypass
:syslck
2.14 l\lemory Usage
room &optional str('am
room prints out a fitirly verhose English description of the virtual memory usage of the
'II.. and some related infunnation. In panicular. one of the things it tells is an
estimation of how much space is left for expansion of the !i"illg heap. ~hich is where aU
ordinary consing is pcrfonncd.
Note also the si:pagefault-count function. pagc 224.
23.5 Time and Date
(See also section 23.2. page 232.)
Nil. provides a set of functions for manipulating dates and timcs. A date and time is .
represented in one of two ways: by a ulliversal-time, which is an integer number of seconds from .-
00:00 January 1. 1900 GMT, and as a decoded time. which consists of the following components:
seconds
minutes
hours
date
month
The one-origined month number: January is 1, etc.
year
The full year, e.g., 1983.
day-of week
The zero-origined day of the week: 0 is Monday, 1 is Tuesday, and 5 is Sunday.
daylighr-sQvings-time-p
t or nil, depending on whether the decoded time is daylight savings time.
timezone
The number of the timclone: 0 is Greenwich time. 5 is Eastern time, -2 is Eastern
European time, and -4.5 is Indian Standard time.
This decoded time is not represented in any datastructure, but rather is returned as multiple
values by functions which decode universal-time, or passed as argument'i as other functions.
MC:NII.MAN:ENV 37
23-DEC-83

NIL Manual 235 Time and I )ate
23.5.1 The Main Functions
The functions in this section arc defined by CO~MO~-I.ISP.
without any package qualification.
and all may be referred to
get-un1versal-t1me
This returns the current time in universal-time fonnat.
get-decoded-t1me
This returns the current time. decoded. as 9 values: the current second. minute. hour.
date. month. year. day-or-week. daylight-sadngs-time-p. and time/one. It is etlccti\'c1y
(decode-universal-time (get-universal-time))
decode-universal-t1me Ullil'('rsa/-/ill/c &optional /il11c:ol1(,
liIllC:UIIC dcl:IlI1t~ to the current timezone (sec page 238). This decodes IIl1ivcrstJ/-liIllC with
respect to lilllc:CJ/lc. and returns 8 \'alues: the second. minute. hour. dale. month. year,
day-of-week. dayliglll-sa\'ings-time-p. and time7one.
encode-universal-t1me seconds III;IIU/C.\ hours dall' 11101l/1i yCelr &optional lil11(':o1/('
tiIllC:OIIC dcf~lllltS to the current [imczone. This encodes the gin:'11 date and time for the
timelone. and returns a universal-time.
23.5.2 Printing Dates and Times
The following functions arc not globali7ed. but must be referred to with the time: package
prefix. Most of them arc the same as those provided by LISP MACHINE LISP. All of them take a
des/illatioll argument. which may be a stream. t. or nil. t means use the value of standardoutput:
nil me4tns return the result as a string. Note that this is compatible with the way the
format function (page 187) interprets its destination argument. not the way the regular NIL
printing functions do. The destination always defaults to t, meaning print the output on
stand ard - output.
time: pr1 nt-t 1me seconds minutes hours da)' month year &optional (destination t)
This prints the specified date and time in brief fonnat, to destination. The fonnat used is
"10/03/83 23:02:59"-the month number, the day in the month, the year (modulo 100),
and the time.
t1me:pr1nt-current-t1me &optional (destination I)
This docs time:print-time of the current time.
1
t 1 me: p r 1 n t - u n 1 ve r s a 1-t 1 me ulliversal-time &optional (destination I) limezone
This effectively docs decode-universal-time on universal· lime and timezone (which
defaults to the current timezone). and then time:print-time of the results to destination.
MC:NIIMAN:ENV 37
23-DEC-83

...
Time and Date 236 NIL Manual
t 1me: pr1 nt-date srcOIu/s minutes hours date month year day-oflhe-week &optional
(deslillatioll/)
This prints the date in a fonnat like
Friday the seventh of October, 1983; 11:02:59 pm
t 1me :print-current-date &optional (deslination I)
Prints the current date. in time:print -date fonnat.
t 1me: pri nt-un 1 versa l-date ul1il'ersal-time &optionaI (deslination I) limezolll'
Uses time:print-date to print tile decoding of universal-time and limeZ()l1e.
time: pr 1 nt - br 1 ef -un 1 versa 1-t 1me ullh'rrsal-limr &oplionaJ (drs/ina/iol1/) rcferc'II('('-/imr
This prints ul1irrrsal-limr in a format likc 10/07/83 23:02. Hnwc\'cr. portions of it wilJ
hc omitted if they are the same· as the corresponding components of the universal-time
refrrencr-/ime (which dcfllllits to the current time). In particular. if the year is the same.
it is omitted. and if the month and day are also the same. the entire date is omitted. So
depcnding on the reference time. one COUld. gel 10/07 23:02 or even just 23:02.
time: p r 1 nt-un 1 versa l-ma i 1-format -date Ullirrrsal-lilllc &optionClI (dCSlilJ(1Ii011/)
Prints thc date and time specified by universal-limr in "mail fnnnat". This is a fnnnat
which conforms to that specified in RFC822. "Standard for the fonnat of ARPA Internet
Text Messages" [6]. It looks like
Fri, 7 Oct 83 23:02:59 EDT
t 1me: pr1 nt-current-ma 11-tormat-date &optional (des/inatiollt)
Prints the current dilte and time. using time:print-universaf-mail-format-date.
23.5.3 Namings
The time package contains a small database of names of months and days of the week. in
various formats. The format is split along two dimensions: the mode. for instance :Iong,
:medium, or :short, and the language. such as :english. There is a global default for each of
these: .
t1me:*default-language.
The default value of this is :english.
time:*detau1t-mode.
The default value of this is :Iong.
Variable
Variable
The mode and language are combined (by lookup) into a composite symbol for which the
lookup of the actual text fonnat is performed. For the following functions. one may specify this
composite symbol. such as :long-engJish. just the mode (:Iong), in which case the default
language is used. or just the language. in which case the default nlUde is used. The three
predefincd modes are :lon9. :medium. and :short. and there are entries for the languages
:english. :french. :german. :spanish. and :itatian. Not all mode/language comhinations are
supported: in particular. :medium is treated as a special case. such that if it is not fimnd. :short
is tried instead. lbc :short mode typically implies the short standard abbreviation: this is usually
three characters. however it· is two for :german.
MC:NILMAN:ENV 37
23'DEC-83

NIL Manual 237 'I'ime and I )ate
t 1 me: mon t h - s t r in g mOlllh &optional f1lodespec
Returns a string naming thc month. in thc fonnat spccificd by mot/l'spec. Assuming the
initial dcfault values for time:*default-Ianguage* and time: *default-mode*,
(time:month-string 12) => "Decembertt
(time:month-string 12 :short) => ttDec"
(time:month-string 12 :spanish) => "diciembre"
(time:month-string 9 :medium) => "Sept"
(time:month-string 9 :short) => ttSep"
time: day-of-the-week-string day-oJ-the-week &optional l1lodespec
Similar:
(time:day-of-the-week-string 1)
(time:day-of-the-week-string 1 :short)
(time:day-of-the-week-string 1 :medium)
(time:day-of~the-week-string 1 :german)
(time:day-of-the-week-string 1 :short-german)
=> "Tuesday"
=> "Tue"
=> ItTues lt
=> "Dienstag"
=> ItDilt
t1me:mode-language-fetch modespec hash-Iable what
This is the primiti\ e v. hich canonicalizes the modc. languagc. or composite symhol into a
compositc symhol, and looks that up in hash-fable. what is just a dcscriptivc string for
error rcporting. e.g.. "Month namc". The two above functions use this function to
retrievc vcctors from thc following hash tables. which arc thcn indcxcd into to gct the
namcs.
time: *month-str 1 ngs*
Variable
This is a hash tablc associating the composite mode/language symbols (e.g., :long-engHsh.
:short-german) with vectors of the strings for the given months. The vcctors are zeroorigincd.
so 1 must bc subtracted from the month number bcfore the aref (or sgvref) is
perfonned. The vectors are always simple general vectors.
time:*day-of-the-week-str1ngs.
The hash table for day-of-the-week names.
Variable
Thus. time:month-string is defined (modulo error checking) as
(defun month-string (month &optional modespec)
(sgvref (mode-language-fetch
(or modespec .default-mode.) .month-strings.
"Month name string")
(1- month»)
Fetching the vector and indexing into it can be useful if the vector is going to be used repeatedly,
for instance for printing a directory listing.
t
~
,..
,.
MC:NILMAN:FNV 37
23-()EC-H3

Time and Date 238 NIL Manu,tJ
23.5.4 Timezones
.t.. mezone. Variable
The value of this is the current timezone. It should be initialized in the NIL site
initialization file to the correct value; otherwise. it will be 5. which is Eastern time.
time: t 1mezone-str .. ng &optional timezolle daylighl-savings-p
This returns the canonical three-charitcter string for the timczone. or nil if the name is not
known to NIl ..
(time:timezone-string 5 nil) => "EST"
(time:timezone-string 5 t) => "EDT"
(time:timezone-string 0 nil) => "GMT"
lill1c:wlt' defintlts to the current timezone. and daylighh~m'il1g.'i-p to the value of
(time:daylight-savings-p).
23.5.5 l\1iscellaneous Other Functions
time: leap-year-p year
Returns t if year is a leap ye,)r. nil otherwise.
t1me:dayl1ght-sav1ngs-p
Returns t if it is currently daylight savings time. nil otherwise.
t1me:month-length month year
Returns the length of the month month in year.
t 1 me : day 1 i 9 h t - s a vi n 9 s - t 1me-p hour day month year &optional limeZOlle
Returns t if the specified dHy/time is in dayJight savings time in the specified time/one
(which defaults to the current timezone). nil otherwise. (The specified hour is assumed to
be standard time.) Note also section 23.5.6. page 239.
time: day-of-the-wesk (day month year)
Returns the number of the day of the week of the specified date.
t1me:ver1fy-date day m01lth year day-ofweek
If day is a day within month which fell on dayofweek. this returns nil; otherwise. it
returns a string describing the conflict
time :moonphas8 &optionaJ ulliversal-time
Returns the phase of the moon decoded into five values: the (zero-origined) number of
the quarter. the day .. hour. minute. and second. The Quarters are (from 0 to 3) new
moon, first quarter, fun moon, and last. quarter. This is presumably the uncorrected
mean longitude.
MC:NILMAN:ENV 37
23-DFC-83

NIL Manual 239 Timc and Date
t1me:pr1nt-moonphase quarter day hour minute second
Prints the phase of the moon in a fonnat like "FM + 2Il3H.29M.57S.". The first field will
be one of "NM", "FQ", "FM", or "LQ". Zero-suppression is perfonned on the other
fields: for instance, "FM + 2D.29M.".
time: pri nt-current-moonphase &optional (des/illation t)
Similar.
Note also the get-internal-run-time and get-internal-real-time functions. on page 223.
2.15.6 \',uiations in nH)'light Savings Time
The timezone objects ~Il. lIses to store information on particular time/ones include a function
which may be lIsed to tell if a particular hour. day. month. and year (when intcrpreted as
sLmdard time) is in daylight time. Most of the initial timezone entries have nil in this component.
which is taken to mean that the zone never uses daylight time. It may be necessary to patch this
up: some functions and hacks arc presented here to aid in this.
t 1me: zoneconv tilll('Z(Jlle
If timezol1c is a timezone object (an object of type time:timezone), it is returned. If it is
a number. then an existing timezone entry for that offset in the list time: *timezones* is
returned.· (Otherwise an error is signalled.)
If the daylight-savings-time predicate ~IL supplies is not appropriate for the site (or is just
plain incorrect). it can be patched by
(setf (time:timezone-dst-rule
(t ime: zoneconv timezone-offset»
'beandorfian-daylight-savings-time-p)
where timezol1e-offsc/ is the offset from GMT of the timezone in question, and beandorfiandaylight-savings-time-p
the predicate which tells whether any particular hour in a particular
year is in daylight savings time.
t
I
I
f
f i
~
I
t1me:regular-american-dayl1ght-savings-t1me-p hour day month year
This returns t if hour, day. month, and year is between 1 am of the last Sunday in April
and 1 am of the last Sunday in October (see below).
t1me:last-sunday-in-apr11 year
Returns the day of the month on which the last Sunday falls in April.
t1me:last-sunday-1n-october year
Returns the day of the month on which the last Sunday falls in October.
Computations like "last Sunday in April" are fairly easy to perfonn. To find the last dow day
in a month. find the day-of-the-weck of the last day of the month. and subtract the number of
days it takes to get back to the desired day of the week. For instance,
(defun last-sunday-in-april (year)
(-& 30 (\\& (-& (+& 7 (day-of-the-week 30 4 year» 6) 7»
111C 30 is the last day in April. 4 the month April: 6 is Sunday, and the 75 and arithmetic with
thcm doing modulus stuff. Obviously the arithmetic can be simplified to
~1C:NII.M:\N:ENV 37
23-1)FC-83

Time and Date 240 Nil. Manuitl
(-& 30

,1\ \1..muJl 241 Job/Process and System Information
Iki.:.li.l'C '11 must use the V\1S time to detennine the abso1ute time. get-universal-time (nnd
.," ~,::;c.., y,hich return results based on that quantity. which is just about all the time and date
.' ~ "!,l;" In this ~c:ction) can return an incorrect value. Also. the quantities returned by elapsed-
• _ .• ~.. I,
t'rT".~ 'r. 1 F 22)) Jnd get-internal-reaJ-time (page 223) are based on this. meaning that if a shift
'~, l"~ (lut of daylight time occurs and the VMS base time is changed, elapsed time measured
.:', '_ ~,J the shift will be incorrect. There is a variable provided for telling NIL about two potential
\. -';,'-;.-v. ide COO\ cntions for bypassing this son of 10ssagc.
t 1:1e: • sy s tem- time - k 1 udge*
Variable
'I hI'-. ma~ take on one of three values,
nil This is the default. It means that the \'\is hase time is al\\'ays the local time
(r()[('ntially daylight time). and hence subject to complete lossage.
:standard
This means that the \'\1S base time is always based on the standard time for the
current timclone.
:gmt
This means that the \,\15 hase time is GMT (implies never daylight time).
f'l:hcr of the last two options eliminate the amhigous·hour and incorrect-elapsed-time
r11 ·hkm' \\ hich might bc suffered otherwise. Of course. they mean that all the \\1S
uulJ[i~~ v.hich show dates and times won't work quite right. Oh well.
I !~,: .1!1(1\ e \41flable is examined for conversion of all \'MS internal times into universal time.
\~..: ::\ \!~.::l~. fllr interpretation of the current time, if the ahove variable is nil. then the
: ' : _:,::~' :\,f,;.. ll: ii,li"I"I(" is ~xdji"dlh:;d. (Thj~ is d lugi\.ai ll.tllU': u~\.:Jhh:f1ll1.:J by Cili.tO~IlCl ~(Jrlware
,:

Job/Process and System Infonnation .
242
NIL Manu

Nil. Manual -243 (\Hnpilation
24. Conlpilation
lompilalion is essentially the process of translating from one specification into another which
is presumably more cfficient. and probably more low-level in some respects. The ~IL compiler
translates LISP code into the VAX instnlctions neccssary to execute that code: some of these
instructions may perfonn the task directly, while others may call functions or 1'\11. kernel
subroutines to do it. In any event. the end result is intended to exclude the ~II. interpreter from
thc running of the program. The ~II. compiler does not output \iACR032 code or anything of the
son: rather. it represents the code and data itself. and assembles the code. liSP objects
referenced hy the code. and whatever other infonnation is needed to help construct that data.
into a cOlI/pi/rc/ codr l11udule. This is what the module daw type represents.
\\'hen the 'II compiler compiles a file. it first estahlishes the proper eJl\ironment for the
compilation. as specified hy the file's attrihule list (described in section 19.8.6. page 205). That
done. it reads and processes each fonn in the file. What it docs with each fonn depends on what
the fonn is.
( pro c 1 aim del-Sptc )
If the yalue of the fOl1n dcl-sprc can be detennined at compile-time. then the compiler
will attempt to assert that proclamation for at least the duration of the compilation. Sec
proclaim, page 46.
(dec 1 are {dcP·spec}.)
The del-specs are processed. and L1Ke effect for at least the remainder of the compilation.
ut=dare ill uli~ UHllCXl i~ son of iikc prociaim with muitipic unevaiu3tea arguments:
howe\er. this usage (non-local declarations) of declare is being phased out and subsumed
by proclaim. It will be probably bc supported indefinitely. and will also be accepting
certain MACLISP-sty]c declarations which proclaim will not.
(eva l-when k ... -J-lisl [onns . .. )
If compile is a member of kwd-lisl. all of the [onns are evaluated then and there. Then,
if load is a member of kwd-list. the [onns are recursivcly processed.
(progn fonns . .. )
fonns are recursively processed. Note that this is identical to (eval-when (load) fonns ... ),
and upwards-compatible with the MACLlSP (progn 'compile fonns ... ) hack.
(ccmp i 1 e r-l et bindings forms • .• )
Establishes the bindings specified by bindings. then recursively processes fomls in that
environment. See page 245.
( de fun Ilame argUst etc . .. )
(defun (name property-name) arglist etc ... )
The function is compiled, and the appropriate assignment (function cell or putprop) will
be put in the compiler's output file.
( de f mac r 0 name etc.. . )
(macro nall1r lambda-list etc ... )
Thc specified macro definition for name is added to the compilation environment. Then.
the macro is compiled. so will be there when the compiled output file is loaded. It may
not be depended on that name is defined in the liSP environment itself: only that code
MC:NII.MAN:COMPIL 37
23-I)EC-83

Compilation 244 Nil. Manual
being compiled will have the macro run to produce the expansion. If it is necessary for
the macro to actually be defined (perhaps in order for it to be called from within other
macros, as opposed to just expanded in code. being compiled). then the defmacro or
macro fonn should be enclosed within an (eval-when (compiJe ... ) ... } fonn.
(defun name macro lambda-list etc .. • )
Ine compiler whines at you and turns this into macro. This is provided to catch old
MACUSJ> code which should probably use defmacro (or at the very least macro) instead.
( de fun l1a1llP fe x p r lambda-lisl elc .• • )_
"1l1e compiler barf.~ at you and turns this into a special form definition. Calls to it from
compiled code wil1 not work. If name is only around f(lr users to caliintcracti\'cly,
howe\'er, it might just function properly. This is provided only to brute-fi)ree through
some ~f:\U IS]> progr~tms. General1y. speci~ll fonns or frxprs should be rewritten as
macros.
( def u n Ilame alom elc ... )
The function definition is assumed to be a MACI.ISP lexpr. It is transfonned appropriately,
and compiled. after the compiler gets through giving yuu a hard time.
(defflavor etc)
Code to perform the flavor definition at load tin;~ is generated. Additionally. declarative
information is added to the compilation environment so that defmethods will compile
correctly, and the routines defined for the :outside-accessible-instance-variables can
be compiled correctly.
(defmethod etc)
Compiles the code for the defmethod.
a1lyth illg-else
If anything-else is a macro caU or a call to a function the compiler has special rewrite
information about, the macro expansion or rewrite is performed~ and the compiler tries
again. Otherwise. anything-else will be evaluated at load time. Currently this i~ done by
compiling the expression. which eliminates load-time dependencies upon macros.
There are various other fonns which implicitly do compile-time processing by vinue of how they
are defined. rather than by the compiler recognizing them specialty. For instance, defstruct
(currently) by default expands into the appropriate macro, function, and data definitions, with
appropriate use of eval-when. For this reason, the above list cannot be taken as being allinclusive.
compile-file input-Jile &key package sel-dejaull-palhname oUlpul:/ile dejiluil-pathname
defaults
Compiles input-jile, storing the vasl file in output-jile.
If package is specified, then the file is read in in that package, in spite of what might be
specified in the source file propcny list (see section 19.8.6, page 20S).
The input-file is defaulted from the dejaull-pallmame if any, and then from dejQuils.
which should be a pathname defilUlts. If sel-dejiJull-palllllame is not nil. then the default
pamname of defoulls (which defaults to the value of .toad-pathname-defaults., page
201) is updated.
MC:NII.MAN:COMPIL 37
23-DEC-83

NIL Manual 245 Compilation
OU/pul-file defaults to illpu/:/ile with a vasl file type (VMS extension of VAS).
By special dispensation (to those of me who cannot get out of the habit of using this
feature), if exactly two arguments are given to compile-fife, then the first is the input file
and the second is the output file. This is typicaUy used like
(compile-file "[nil.io]iofun" "[nil.vas]")
The CO:vt:vtO~ LISP definition of compile-file accepts only the keyworded argument outpu/­
file.
comfil e ...
Alternate name for compile-file. CO\1\fO~ LISP defines the use of the name compilefile.
hut not comfile, f(lr whatcver that is wonh. .
compil e jUllction
Compiles the interpreted (and in-core) definition of jUlic/ioll, in-core. That is.
(defun fact (x)
( i f (z e r 0 p

Intcraction Control . 246 NIL Manual
switch. and these arc now obsoleledby usc of the optimize declaration. compiler-let is
still useful. of course. for communication between macros. and that is its intended usc
anyway.
24.1 Interaction Control
compiler: .messages-to-term1nal?
Variable
If this is not nil. then the compiler (compile-file and compile. and cvcn the I.SB-defincd
function Isbcl [4}) will print out verbosely on thc terminal. If it is nil. nothing will bc
printed. unless crrors occur. which is a separate can of worms. By default. this is t.
24.2 Efficienc),'t Optitnilation .. and Benchmarking
The current :,\11 compi1er is incredihly stllrid in some ways. 8asically. it is an o\"crgrown
one-pass code generator: it takes in a USP program. and spits out VAX machine language.
m~lking liberal usc of LISP function calls and speciill subn.dtincs to handle things which arc too
hulky or too complex for it to cod

NIl. Manual 247 Efficiency. Optimization, and Benchmarking
to briefly describe it more generally. Basically, a function call is handled hy the caller "creating"
a call frame on the stack, filling it in. and then perfonning the actual call. When such a frame
is created, it can be recognized as such by a debugger (the current one doesn't know beans about
it. but that is beside the point). and. while the arguments are being computed. it is possible to
ten not only what function is aboul to be caned. but which arguments to it have been computed
(and what their values are). and which have not. If the compiler decides that it is ok to not have
quile this much debugability. it might decide to try to compute some of the arguments as it
creates the function call argument frame-this can save both space and time. but means you
cannot tell what is going on while it is happening. No matler which way it does this. it may still
have to push varying length blocks of constants on the stack. Even herc. therc arc spacc/time
tradcofls to hc made: for instancc. helow some threshold. it takcs long.er to do a block -movc
than to do a series of movcs/pushcs. And. therc is a decision as to what constant it is that gets
pushed: a marker (rccognizable by the debugger). or just zeroes (which can be done more
efficicn t I y).
Another area is that of ccrtain functions which can bc inline-coded. but which arc nonnally
too hulky (0 make it worthwhilc under nonnal circumstances. memq is a finc example of this.
Nonnally. memq is a minisuhr which will give a correctahlc crror if thc list is not a proper list.
and which will detect circularity. If specd is myc important th,1I1 space and safety. however. the
compilcr can in line-code the loop. Thc exact detennination is not only a filnction of the qualities
specified with optimize. but also the particular circumstances. If the list argument to memq is
known at compile time. then the compiler can verify that it is a non-circular proper list. and thus
no longer has to worry about the "safety" of the call. I f in addition the memq is being used for
"plcuil:alC vaiuc·'. lhal is. in a comeXl iike
( if (memq item lisl) liJell-do-lhis else-dc-this)
whcre the specific value of the memq does not matter, then the compiler can just code out the
proper series of eq checks. How many it will be willing to do this for. is once again a
space/time tradcoff.
There is another class of optimization which can be perfonned: that is unfolding of common
cases out of a more generic routine. For instance, the 1 + and 1- functions (page 74) are coded
as minisubrs. They arc fairly generic, since they can accept arguments of any numeric type. But
a common usage is with arguments which are fixnums. If space is not considered particularly
important. but speed is. then the compiler can check to see if the argument is a fixnum. and if
so do the addition or subtraction itself without getting into the generic routine. Because the code
only does this on things it has verified as fixnums. and because it checks for overflow. this
particular optimization does not involve "safety",
Another aspect of "safety" is how likely the operation being perfonned is to produce
something "illegal": in a LISP implementation like NIL. many objects like fixnums and characters
have their data represented in the pointer. and operations on those objects just do operations on
the pointers. For certain trivial operations. of which many of the character functions (chapter 11)
are characteristic, the compiler might choose to produce code which is a bit more circumspect
ahout what it docs with pointers. what data-types of objects it might generate if given erroneous
inputs. or possibly even whether it inline codes at all. depending on what the result of an
erroneolls input mig.ht imply. Take. for example. char-upcase: if this were inlinc-coded (it
might not be in this particular version of i\1L). it effectively would be replacing part of the
"address field" of the pointcr which is its argument. by something elsc. If that argumcnt was not
a character. but (say) a vector, it is quite likely that the resultant object would be unprintable.
MC:NII.MJ\N:COMPIL 37
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Ftlicicncy. Optimi/alion. and Benchmarking 248 NIL Manual
givc garbage whcn examined. and. assuming the existence of a garbage-col1ectoT. cause the
garbage-collcctor to fail in the middle of its operation. leaving thc LISP totally useless. Many
operations of. this nature. while having a moderate amount of overhead if done as function calls
with error checking. can be made to at least not return such objects with only a trivial overhead.
\\'hiIc in a sense this masks errors rathcr than detects them. having your lisp gct blown away by
an iIlegal pointcr does not facilitate debugging either. In this regard, the things which heed the
safety optimization quality will gencrally not inline code at all (depending on their triviality) jf the
safcty quality is set to 3. (Also. in gencral. only high-level routines might offcr this choice: the
:\11 fixnum-only routines. and character "subprimitives". will always inline-code. and not offer this
safcty "option".)
Thcrc ,Irc \·cry fe~' things which rccognilc thc compilation-speed optimi/

NIL Mdllual 249 Illlroduction to thc STEV E editor
25. Introduction to the STEVE editor
25.1 Introduction
STEVE is a general purpose screen oriented text editor based upon the EMACS editor. In many
respects STEVE and E\1ACS arc identicaL with the primary difference being that STEVE is written in
Nil. for the DEC VAX -11 series computers and can be called directly from the i'll. interpreter.
Those who arc familiar with EMACS will be able to usc STEVE immediately, and should skip to
the end of this chapter, as the first part is meant to be an introduction to STEVE.
25.2 Getting Started
There is one diflcrence hetw.een the editor environment and the rest of '" to he aware of.
IkGllI~e the editor and \"\1S ha\"c conflicting uses for many of the control keys. the editor must
nm in "passall" mode. This implies tJlat the nonnal interrupt cmrmands do not normally work in
tJle editor. So the first command to learn is tile ediLOr command to return to \\!1atc\er you \.\ere
doing hefore you entered the editor. It is a two key command typed hy holding down the
"Control" ke) and pressing the "Z" key twice.
Control-Z Control-Z Return-to-superior.
Exit tJle editor and return to whoever called it. This is tJle nonnal way to exit from
STFVE.
Now that you know how to exit the editor you may be curious how to enter it. Of course
tJlis is not an editor command, but ratJ1er a 1'lL function.
ad &optional whal-Ia-edit
Enters the editor, returning to whatever you were working on before. If you have not
run the editor since starting NIL it will be completely initialized with one empty buffer.
or
Normally one types (ed) to the NIL interpreter to get into STEVE. what-ta-edit may be a
path name (or string naming a file), or the name of a function. If given, the editor will
try to find the file or function definition and let you edit it: otherwise the argument is
ignored. There arc editor commmands to find files and function definitions anyway, so
the argument is not really very importan~ except that it can be convenient. and can be
used from programs.
MC:NILMAN;EDITOR 18
23-DEC-83

Editing Files 250 NIL Manual
25.3 Edit i ng Files
The principle purpose of an editor is to create or modify a file. In broad outline an editor is
used by reading a file into a buffer. modifying it somehow and then writing it back to some long
term storage device. generally a disk. Most of the editor commands arc concerned with modifying
a buffer. and will be expained later. In order to understand the commands for reading and
writing files one should know about the general structure of STEVE and its buffers.
I NIL I
I Editor I
I \
I \
J Buffer-l I
I Buffer-2 I
I File-l I
I File-2 I
As the diagram shows. the editor runs inside Nil.. and contains any number of buffers, each
of which is associated with a file. This diagram can be modified by creating a new buffer or
kiHing one, or by changing the file associated with any buffer. There arc editor commands for all
of these operations. and for some more complex combinations of them. The editor always selects
one buffer as the current buffer, and displays a section of it around the cursor.
The fonnat of this display is· one of the features of an EMACS style editOr like STEVE, and is
the reason it is called a "screen editOr".
MC:NILMI\N:EDITOR 18
23-DEC-83

Nil. Manual 251
Editing Files
This is a picture of what an editor I
display might look like except that is is very'
small. ,
Note that the cursor is at the end of ,
the previous paragraph. ,
I
I
I
STEVE foo (LISP) disk:[cre]bar.lsp {3} --. I
I
I
The hox in the diagram represents tllcedgcs of a ternlinal screen. The two paragraphs are
thc contents of a huffer. The single line below tllat is called the mode line. It contains as l1Hch
in f'(mnation ahout the currcnt sUite of the cditor as is convenient. From tllis we see that tlle
buffcr is named "foo" and that it is associated with the file "disk:[cre}bar.lsp". The notation {3}
after the file name indicates that the current version number is 3. If the file does not exist on
disk the version number and tlle braces will be missing from tlle mode line. The star (*) on the
right of the mode line indicates that the buffer has bcen changed so it is not the same as the file
Oil Ul~~. Tile \.:Uln:1ll po~ition uf the cursor is at the end of the first paragraph. (On most
tenninals a cursor shows up as a blinking underscore or box. though this depends upon tlle exact
type of tenninal. In this chapter we show the cursor as a underline (-) since it is fairly difficult
to print a blinking cursor.)
Under the mode line is a blank area of several lines. This is called the mode area and it is
where most error messages and prompts are shown.
We are almost ready to start expaining the individual editor commands. The only other thing
you should know first is how they arc typed. Most STEVE commands are either one or two
character commands. Since one adds alphabetic characters to the buffer simply by typing them
(not that you know this yet) STEVE must not use alphabetic characters for its commands. Instead
the control characters are used. (The control characters are typed by holding down the "control"
key and pressing some other key, just as the capital letters are typed by holding down the shift.
key.) Since there are not enough control keys for all of STEVE'S commands it also uses a meta
key. A Meta key is similar to a shift key or a control key. Now we can have the characters Ha U ,
"A", "Control-A", "Meta-A", and "Control-Meta-A".
Unfonunately most terminals do not have a meta key. Not to worry, though, STEVE is
designed to work without i~ just as certain text justifiers are designed to work with tenninals
which have no lower case. Three commands are "bit-prefix" commands. Typing one of these will
change the next character you type just as if you had been holding down the corresponding
combination of control and meta keys.
MC:NII.MAN:EDITOR 18
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. -'- .:.-- - ... .. - ,-,:,. . ~ . ,~.- .
·,,:.':'. ,;~, ~~ ~i~~£~~~)' ::~' ," .":: ":,,.:~: ,,' , ' .

Editing Files 252 Nil. Manual
Altmode
Prefix~Meta
Pressing Allmode (marked SELECT or ESCAPE on some terminals) will make the next
character a "meta" character. For example Allmode F(two characters) is the same as
Aleta-F (one character).
Control- Prefix-Control
A
Pressing Control;. t (control-uparrow) wilJ make the next character a "control" character.
For example Control-t F (two characters) is the same as COlllrol-F (one character). On
some terminals. notably the vnoo. ((mtrol-t is typed as ('olllrol-- (control tilde);
normally. the A character is a shifted 6. so one holds down control, shift, and 6.
Control-Z Prefix-Control-Meta
Pressing ('emlrol-/. will make the next ch41r41cter be both a control and a meta character.
For example CUll/rol-/' F (two characters) is the s.lnle as COlllrol-Alela-F (one ch~lracler).
All of these bit-prefix commands add the quality to the next character. There is no problem
with doing it twice. The two character sequences COlllrol-ZZ and ('oll1ro/-7. ('o11lrol-Z both 4lre
read as ('olllro/-Alela-/..
We are now ready swrt expaining the various editor commands. These are the commands you
will use to create buffers and write files. All of these commands arc safe to use since they will
notice if you are about to destroy any of your work and ask you if you really want to do that.
Control-X Control-F Find-File
Find-File will prompt filr a file name and you should type it from the keyboard. If there
is a buffer for that file then it wiU be selected and be the new current buffer. Otherwise
a buffer is created for the file and the file is read in from disk if it exists there. Find­
File is the most common way to read a file from disk. It creates a new buffer for each
file which is convenient. When Find-FHe creates a buffer it lIses the file name without
any extention as the buffer name. Since the name of each buffer must be unique this
docsn't work when you are editing two files which have the same name but are on
different directories or have different extensions (file types), so Find-File will notice if you
are doing this and will ask you for a new buffer name to use.
Control-X Control-S Save-File
Save-File . writes the current buffer to its associated file, and changes the mode line to
indicate that the buffer and file are now identical. (This is not done until the output is
complete. so if there is a disk error or some other error you will not think it has . been
saved when it hasn't been.)
Control-X Control-V Visit-File
Control-X Control-R
Visit-File is 1ike Find-File except that it re-uses the current buffer. destroying its contents.
It is still safe since it will·offer to save it if any changes have been made to it
Control-X Control-W Write-File
Write~File writes the current buffer to a file, but .unlike save file it wi1J prompt you for
the file name.
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NIL Manual 253 Editing Files
As an example. suppose that the screen looks like the diagram ahove. If you type Colllrol-X
COl1tro/- H' (\\'rite-File) the editor will prompt you for a file name. Assume you want to save the
file into disk:[cre]baz.lsp. You type "disk:[cre]baz.lsp". The screen will look like
this:
This is a picture of what an editor
display might look like except that is is
small.
Note that the cursor is at the end of
the previous paragraph.
STEVE foo (LISP) disk:[cre]bar.lsp {3} -- •
Write File:disk:[cre]baz.lsp_
I
I
verYI
I
I
I
I
I
I
I
I
I
I
Notice that the cursor is temporarily placed in the mode area. After the command is
complete it will return to the text in· the buffer. The editor will fill in an incomplete file
specification for you. using the file specification associated with the huffer. In this example the
liic mum.:

Modifying the huffer 254
Nil. Manual
This is a picture of what an editor I
display might look like except that is is veryl
small._
I
Note that the cursor is at the end of I
the previous paragraph.
I
I
I
I
STEVE foo (LISP) disk:[cre]bar.lsp {I} -- I
Wr it in 9 F i 1 e . . . I This lil1l' ...
Wr i t te n SAl. LSP : 1 [CRE ]01 SK :
I Theil litis line
Nolice thal the cursor has returned to the huffer text ~Uld that the star (*) has been removed
from the mode line to indicate that the buffer and file arc identical. and that the version number
h'l~ heen changed to 1. This is because the new file name did not exist on disk. Had the file
been sm ed under its old name the version number would have been incremented by 1 from 3 to
4. Finally the file name in the mode area has been updated so that Save· File wm usc the new
file name.
25.4 l\lodifying the buffer
25.4.1 The Simplest Commands
As I hinted before. typing any alphanumeric character will add it to the buffer. In fact
almost any character that you can type without holding down the control key will act like this.
Also, the delete (or rubout) key will delete the last character before the cursor. If you can place
the cursor where you want it and delete· and insen characters then you are already able to make
any editing change you have to. Since it is so simple to change characters in the buffeT, STEVE
concentrates on commands to put the cursor where you want it quickly and easily. The first few
such commands are:
Control-F Forward-Character
COlllro/-F moves the cursor forward one character in the buffer. (The end of a line
counts as one character.)
Control-B Backward-Character
{ontrol- B moves the CUrsOT backward one character in the buffer.
Control-N Down-Real-line
Move straight down to the next line.
Control-P Up-Real-line
Muve straight up to the previous line.
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NIL Manual 255 Modifying the buffer
These are the commands to. move up down right and left.
Now you know how to edit a file! If you can you should probably try to use STEVE to create
a simple file and save it. Print it if you can and compare it to what you see on the screen. See
what happens if you try to back up before the beginning of the buffer using Colllrol- B or
Control-Po Type enough lines to fill up the screen (use Return to end each line) then a few
more. What happens when the cursor is about to move onto the mode line? Now usc Control-P
to move back.
25.4.2 Now that you know the Simplcst Commands
Now that you know the simplest commands there are many others that you should learn.
There are some general facts ahollt ti1e editor which will help you get more out of each command
which 1 will expain first.
25.4.2.1 Numcric Argunlcnts
It is possible to give any command a numeric argument. The command or may not lise it.
but you can always supply it. In fact, if you don't supply an argument an argument of one (1) is
implied. There are several ways to specify an argument. In all cases the numeric argument is
typed before the command. The most general way to specify an argument is:
Univer!al-Argument
COlltrol-V followed by a positive or negative integer specifics ti1at integer as the argument
for tile following" command. Cvmrul-V with no number specifics an argument of four (4).
Control-V Alillus with no number is treated specially as an argument of minus 1 (-l).
Some commands treat Control-V with no number differently than Control-V 4.
For terminals with a meta key it may be easy to usc the meta-digit keys.
Meta-O, Meta-I, ... , Meta-g, Meta-Minus
Control-Meta-O, ... , Control-Meta-g, Control-Meta-Minus
Auto-Argument
Any of the Metafied numeric digits begin a numeric argument. It is just like Control-V
followed by the digit. Notice that repeated meta digits are multiplied together.
Control-O, ... , Control-g, Control-Minus
Auto-Argument-Digit
The control-digits end any previous digit and act as digits in an argumenL Thus Control-2
Co Iltrol-3 is the argument twenty-three (23). Any arguments before or after a sequence of
control-digits will be multiplied by the final control-digit argument. Because most
terminals do not send control-digits these must be specified using the uparrow bit-prefix
(for instance, by typing Control-' 2), so in practice they are not used much. Note that
the Control-'sI illus must be specified first
If several arguments are specified they are multiplied together. The primary use of multiple
arguments is to type Control-V severa) times in a row. r .. ach Control-V multiplies the argument
by four (4). So lOll/rol-V COll/rol-V is sixteen (16) and lVlltrol-V lOll/ml-U Cuntrol-V is sixtyfour
(64). The. cursor movement commands treat the argument as a repeat count (as do most
MC:NILMAN:EDITOR 18
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Modifying the buffer 256 NIL Manual
commands where that· is me:.lningful). Some useful combinations are {olllro/-U ('omra/-V
('(Jlltra/-F which moves forward about a quarte~ of a line, and COIl/ro/-V COlltro/-N which moves
down four Iines~ You will. find many other "Cliches" or combinations of editor commands which
you use automatically to do one thing.
25.4.2.2 Contro)-X
As I said bef(lfe there arc not enough keys on a keyb~ard tbr all of the commands. defined in
STF\,J.:. The Aleta key is one way of getting more characters so STFVF can have a Jarge number of
single character commands. But it is not enough. To get e,"cn morc commands STF\T uses the
key COlltml-X as a prefix chara

Nil. Manual 257 Modifying the buffer
If you type a question mark (7) while typing a Alcta-X command you will see a list of all
possihle ways to finish the command. This is typed in the upper part of the screen, over the text.
(As soon as the Aleta-X command is finished. the text will be re-displayed.) If the list is longer
than one screen fu 1 the word to. mo r e ." will appear on the last line above the mode line. Type
5;pace to see the next screenful of commands. Type COlllrol-G to abort the entire Afela-X
command. (There are several other commands which use the upper part of thc screen
temporarily. All of these will print to.more." in the bottom line and expect either a ... S·pace to
continue. or a COlllrol-G to abort. Any other character causes an abort. and is then used as a
command.)
A summary of special ,\I ela- X characters.
Delete
E"icape
Space
Control-G
Control-W
Control-ll
?
Ruhout the last character showing in the command.
Completes the command and separates arguments.
Completes a word.
Abort everything.
Rubollt a word. Works while typing arguments also.
Start over. Rubout the entire Meta-X command. (Doesn't abort.)
Help.
Most commands which are nonnally executed using AINa-X are smart about their arguments.
They can dctenlline how many you have typed and will prompt you for any that are required.
Often it is easier to use ,Urla-X commands this way since the prompt will tell you what kind of
urgumcnt hi typc. Si.iiiiC commands can d,,) cliinpkti(iil flif Y\JU "if ,,)ihcrw b(: hdp you lY 1-'(: tli(:
arguments. The C()l1lrvl-JUela-X command is a variant of Alcro-X which is designed to lake
advantage of this. The difference is that the command is executed as soon as it is completed,
either by Escape or Space. Otherwise it is exactly the same as Alela-X.
25.4.2.4 ~farks and Regions
Associated with each buffer is a ring which may store up to eight (8) marks. These are buffer
pointers created by certain commands for future reference. There is a command to create a mark
where the cursor is and a command to go to the last mark. and some other commands .. The text
between the cursor and the last mark is called the region. Many commands operate on this
region.
25.4.2.5 KUling and Un-killing
Whenever more than one character is deleted it is stored in a place called a kill-ring. Should
you decide that it was a mistake to delete it then you may retrieve it with the un-kill command
(Conlroi- Y). This also lets you copy text from one place to another, by killing it. moving the
cursor and then un-killing it. To make severa) copics type COlllrol- Y scveral times. The
command un-kill-pop CHela- Y) will retrieve thc next to last peice of killed text. If A/r/a-}' is
used right after lO1l1r(J/- Y or Alela-r the previous un-kill is deleted first (Unlike ns E\1ACS.
Alela- r can be used at any time.)
MC:NII.MAN:E))ITOR 18

M(~or Modes 258 Nil. Manual
25.4.2.6 List Oriented COlnmands
A number of commands operate on "lists", These are nonnally defined as LISP lists with
balanced parentheses. This definition is controned by a syntax table and may vary in different
major modes (see below). For example. in l.sa mode the characters { and } are· a type a
parenthesis and will define a list The editor knows about doublcquote syntax for strings and
vertical-bar syntax for symbols,
25.4.2.7 *more*
A number of commands will overwrite the text on tJle screen, There is no need to worry.
the text has not changed and will redisplayed when the current command is finished. If this
merwrite fills the top part of the screen tJlen the word u.more." will be primed on tJle line
above the mode-line. The editor will wait for you to rend tJle screen and type a space. The
space will not be put into tJle buffer. it just indicates tJlat you arc ready to see me next screenful
of informatio"'l. If you type lOl1lro/-G it will abort ~see below),
25.4.2.8 Aborts
When the editor is reading from the tenninal it usually will abort if you type l ol1trol-G. lbe
word "aborted" will appear in the mode area. This is a good thing to try if you are losing.
though it doesn °t work in some places it should.
25.5 Major Modes
When editing different kinds of documents it is often convenient for some editor commands to
behave slightly differently. For example, when editing a program it seems most useful to have
the Tab key indent the current line so it lines up with the corresponding syntactic unit above it,
but when editing a paper you want the tab key to indent for a paragraph. STEVE has a number
of major modes which are designed for special kinds of editing. Most of the major modes are
very similar, so there is no need to relearn much when you change modes.
Bolio mode
A mode bujJt on Text mode (see below) indendcd for sources to the text justifier Bolio,
Knows about Bolio comments. Also assumes that Bolio is being used to document a Lisp
program. so the paren echo hack is turned on and AI eta-. tries to find a function
definition. The Control-Meta digits are used to change to that number font. Control­
AI eta-· insens a "pop font" command.
FUndamental mode
The basic mode upon which most other modes are built Not used for much editing,
since usually there is a better and more specialized mode for any particular job,
Lisp mode
For editing LISP programs. The principle features are that parentheses arc matched as
they arc typed (try it. it is hard to explain) and that the Tab key knows how to indent
for LISP code.
MC:N1I.MAN:EDITOR 18
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, ,
...:.: ::/~ "~\.~~·i;.:. ~,., __ ..~..

NIL Manual 259 Help and Self" I )ol'lllnentation
LL mode
Lisp Listener mode is not really for editing documents. It simulates the liSP (or !'\IL) top
level loop by evaluating each top level fonn as soon as it is typed, and printing the result
into the buffer. There are several reasons to use this mode for interactive testing.
Because you are typing at the editor you have its full power to modify a form as you
type it in. You are not limited to deletcing the last charactcrs typed as you would be
nonnally. Even after a fonn is executed you may modify it and re-use it by backing up
(with COlltrol-P), editing it, and then re-executing the fonn with !..tela-/. or by erasing
and re-typing the last close paren. Finally. there is a record of what you have done. and
the results. You may save the buffer mid print it. You may add comments as you work.
LSB mode
For editing I.SB program~. The primary difference from 1 -isp mode is that the characters {
and } arc also treated as Parentheses.
Test mode
This should be dyked out. It is not useful except for debugging the editor itself.
Text mC:',e
For editing english (or german or french .. ,) text. T(lb is 1101111411 and ,Hela-. only searches
the loaded buffers without trying to find the source file through the function definitinn.
Obis may be wrong... comments?) Paragraph commands search for lines which begin with
a white space character rather than for blank lines (as they do in program modes.)
25.6 iieip and Seii Documentation
STEVE has a several commands designed to hclp you when you don't know how do something.
The principle commands are Alela-? and COfllrol-Aleta-? which is the more general of the two.
\\'hen you type {Oil trol-AI ela-? the editor will prompt you in the mode area with:
Help (type? for options):
You respond with a single character. The choices are
A Apropos. (You type a Word to search for.)
C Document a Character. (You type the character.)
o Describe a command. (You type the command name.)
K Document a Key. Identical to C.
S Syntax. (You type a character.)
A (Apropos) prints all paragraphs in the help file which contain a string.
finding documentation on some concept. Also available through AI ela-X Apropos.
It is useful for
C (Character) finds the name of thc command that a key is bound to and then treats that just
like D (Describe) would. Also available through Aleta-X Describe-Key. (Type the full name.
AI ela-X Describe confuses completion.)
U (Uescribe) searches for a paragraph in the hclp file which contains the string in the first
line of the paragraph. The help file is structured so that paragraph will he the documentation for
that command when it is fully typed. If this is losing because you don't know the fun name of
the command try Apropos instead. Also available through AI eta-X Describe.
MC:NII.MAN:EDITOR 18
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Glossary ofCommclllds 260 NIL Manual
K (kcy) is anothcr namc filf C (Ch

Nil. MmlUal 261 Glossary of Commands
Glossary Of STEVE commands
25.7.J Special Character Commands
Backspace
Backward-Character
Move the cursor backward one character or more if given an argument.
Tab
Insen a tab.
Insert-tab (In non-LISP modes)
Tab
Indent-For-Lisp (In LISP modes)
Indent tJle current line according to the nesting struclUre.
Linefeed
linefeed
Break the current line and indent the next line. Equivalent to Rl'IUfll followed by Tab.
Return
Crlf
Insert a line separator or just move. to the next line jf before two blank Jines.
comme'1t ender if there is one.
Altmode
Bit-Prefix Meta
Make the next character be a Alela character.
Skips
Rubout
Backward-Delete-Character (in non LISP modes)
Deletes one character before point. If given an argument kills that many characters before
nnint
r •.-.•-
25.7.2 Control Character Commands
Control-Altmode Exit-Editor
Return to whoever caned the editor, generally the NIL interpreter.
Control-Space
Set-or-pop-mark
With no argument places a mark at point. With an argument pops the last mark and
goes to it
Control-;
Indent-for-comment?
Inserts a comment on the current line or adjusts the placement of an existing comment.
Control-<
Mark-Beginning
Place a mark at the beginning of the buffer.
Control-=
What-Cursor-Position
Prints the X and Y coordinates of the cursor on the screen, the current character and the
number of characters before point and the percentage of the file which that is. Line
separators count as two characters since that is how many they occupy in a file. See
Count - Lines - Region
Control->
Mark-End
Place J mark at the end of the buffer.
MC:NILMAN:EOITOR 18
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c
Glossary of Commands 262
Control-@
Set-or-pop-mark
With no argument places a mark at point. With an argument pops the Jastrnark and
goes to it.
Control-A
Beginning-Of-Line
Move the cursor to the beginning of the current line.
Control-B
Backward-Character
Move the cursor back one character or more if given an argument.
Control-C
Exit-Editor
Return to whoever called the editor. generally the ~Il interpreter. CCJIllrol-C should
inlerrupt ule editor as it docs in the rest of 'II. but because the editor must be in Passall
mode that is not possible.
Control-D
Delete-Character
I :>C1ete the character that the cursor is on.
Control-E
End-Of-'.ine
Mo\'e the cursor to the end of the cunent line.
Control-F
Forward-Character
Move the cursor forward one character or more jf given an argument.
Control-G
COlltroJ-G will abort the editor if it is reading from the terminal.
Control-H
R~ckw~rd-C~aracter
Just like Comru/-B. COlllro/-H is Backspace in seven-bit ASCII.
Control-I
Tab
Conlrol-! docs whatever Tab would do. In Lisp Mode and its derivatives (see major
modes. below) this indents according to the syntax of text as a LISP program. In non-Lisp
modes this is a normal Tab.
Control-J
Indent-New-Line
Equivalent to Return followed by Tab. Ends the current line and indents the next line.
Control-K
Kill-Line
Kill to the end of the current line. If the cursor is at the end of a line it kills the line
separator. With an argument kills that many lines.
Control-L
New-Window
Dear the screen and redisplay everything. Useful if the screen is garbaged somehow· (for
example if someone sends you mail). The window is moved to put the cursor in the
middle of the screen. With an argument puts the cursor that many lines from the top of
the screen. With a negative argument counts fTomthe bottom of the screen.
Control-M
CRLF
Insert a line separator or just move to the next line if before two blank lines. Skips
comment ender if there is one.
Control-N
Down-Real-Line
Move the cursor straight down one line or more if given an argumenl
Control-Q
Open-Line
Puts a Return right after the cursor. With an argument creates that many blank lines.
MC:NII.MAN:EDITOR 18
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Nil. Manual 263 Glossary of Commands
Control-P
Up-Real-line
Move the cursor up one line or more if given an argument.
Control-Q
Quoted-Insert
The next character is treated as an alphanumeric character regardless of what it is. This is
how to put control characters into the buffer. Aleta characters cannot be put in the
buffer, because they cannot be in NIL strings.
Control-R
Reverse-I-Search
Incrementally search backward through the buffer for a string.
Control-S
I-Search
I ncrementally search the butler for a string.
Control-T
Transpose-Characters
Exchange the character before the cursor with the character at the cursor.
Control-U
Universal-Argument
Read an argument for the next command.
Control-V
Next-S·.reen
Move the window and the cursor forward almost one scrccnful. The last two lines of l.he
window arc now the top two lines. With a numeric argument moves the window and
cursor that many lines.
Control-W
Kill-Region
Kill the region between point and mark and save it in the kill ring.
Control-X
Prefix-Character
COil tro 1-X is a prefix character. Type any character after it for a two character command.
Control-Y
Un-Kill
Get the most recent kill out of the kill ring and insen it in the buffer. With an argument
N gets the Nth kill. With just Control-Vas an argument. it leaves the cursor before the
un-killed text.
Control-Z
Bit-Prefix Control-Meta
Read the next character as a Control-AI eta character.
Control-\
Prefix-Meta
Read the next character as a Aleta character.
Control-]
Abort-Recursive-Edit
Return from a recursive edit without doing anything more.
Control- ....
Bit-Prefix Control
Read the next character as a Control character.
Control-Rubout
Backward-Oelete-Hacking-Tabs
Like Rubout except that a Tab is first expanded into spaces. This is useful for indenting
things. In Lisp modes Rubout and Control-Rubout are interchanged.
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Glossary of Commands 264' NIL MmlUal
25.7.3 Meta Key commands
Meta-Linefeed
Indent-New-Comment-Line
Equivalent to Control-N Meta-:
Meta-Return
Back-To-Indentation
Put the cursor on the first non white-space character in the current line. (Tabs and spaces
arc white-space.)
Meta-Altmode
Start a minibuffer.
Minibuffer
Meta-#
Change-Font-Word
Change the font of the pre\,ious word~
Meta-(
Make-parens
Enclose the next I.ISI) exprcs..~ion in parens. With an argument enclose that many I.ISP
expressions.
Meta-)
Move-Over-Right-Paren
Move past the next close parenthesis. then do a I.illr/ecd.
Meta-.
Oefun-Search-All-Buffers
Find a defun. In some modes this will look at the subr object to find the module a
grovel around to find and load the file where the function is defined. In most text modes
(other than bolio) it just searches the loaded buffer.
Meta-;
lnoent-t"or-comment?
Inserts a comment on the current line or adjusts the placement of an existing comment.
Meta-<
Goto-Beginning
Put the cursor at the beginning of the buffer.
Meta-=
Count-Lines-Region
Prints the number of lines between point and mark in the mode area. Also prints the
number of buffer characters. between point and mark (counting the line separator as one
character. See What-Cursor-Position.)
Meta->
Goto-End
Put the cursor at the end of the buffer.
Meta-?
Describe-Key
Reads a key from the keyboard and prints its documenta~on.
Meta-A
Backward-Sentence
Move. to the end of the previous sentace.
Meta-B
Backward-Word
Backup one word. (With an argument backs up that many words.)
Meta-C
Capitalize a word.
Meta-O
Kill the next word.
Uppercase-initial
Kill-word
MC:NILMAN:EDITOR 18
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NIL Manual
Glossary of Commands
Meta-E
Forward-Sentance
Move the cursor to the end of the current sentance.
Meta-F
Forward-Word
Move over one word. With an argument moves over that many words.
Meta-H
Mark-Paragraph
Put point at the beginning of a paragraph and mark at the end.
Meta-I
Insert-Tab
Puts a tab into the buffer. Alela-I doe's not change in Lisp modes.
Meta-J
Equivalent to COlllrol-N Afcla-:.
Indent-New-Comment-Line
Meta-K
Kill-Sentence
Kill the sentence after the cursor.
Meta-L
Lowercase-Word
Convert the next word to 4111 lowercase characters.
Meta-M
Back-To-Indentation
Move the cursor to the first non white-space character in the current line.
Meta-N
Oown-Comment-line
If the current line has a blank comment delete it. rlllen move to the next line and add
or adjust the comment start in the correct column.
Meta-p
Up-comment-Llne
If the current line has a blank comment delete it. Then move to the previous line and
add or adjust the comment start in the correct column.
Meta-R
Move-To-Screen-Edge
With an argument move to the beginning of that line on the screen. With a negative
argument count from the bottom. With no argument move one third from the top.
Meta-S
Center-Line
Centers the non white-space characters in the current . line.
Meta-T
Transpose-Words
Exchange the words before and after the cursor.
Meta-U
Uppercase-Word
Conven the next word to all upper case characters.
Meta-V
Previous-Screen
Move point and the window back so the two top lines become the two bottom lines.
With an argument move that many lines.
Meta-W
Copy-Region
Put the text between point and mark in the kill ring but do not delete it from the buffer.
Meta-[
Backward-Paragraph
Move to the beginning of a paragraph. In Lisp modes a paragraph begins with a blank
linc. Otherwise a paragraph begins with a line that starts with a white-space character.
Meta-\
Oelete-Horizontal-Space
Delete any spaces or tabs around the cursor.
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Forward-Paragraph
Move to the end of a paragraph.
Meta~]
Meta- Delete-Indentation
A
Join the current line to the previous line and delete white space as appropriate. Leaves
the cursor where the line separator wa~ . so a Linefeed undoes the effect of AI ela- t .
Meta--
Buffer-Not-Modified
Clears the flag which says the current buffer has been changed. The star (*) in the mode
line wiIJ be erased. He careful with this command: usc it only when you arc slire there
have not been any dMnges to the buffer that yuu want saved.
Meta-Rubout
Backward-Kill-Word
K ill the word befor the cursor.
25.7.4 Control-l\leta Commands
Control-Meta-Backspace Mark-Defun
Put point at the beginning of a defun and mark at the end.
Control-Meta-Linefeed Indent-New-Comment-Line
Equivalent to COl1lro/-N Alelo-,' .
Control-Meta-Return Back-lo-Indentation
Move the cursor to the first non white-space character in the current line.
Control-Meta-(
Backward-Up-List
Move backward to next enclosing open parenthesis.
Control-Meta-)
Forward-Up-List
Move forward to next enclosing dose parenthesis.
Control-Meta-;
Kill-Comment
Kill the entire comment field on the current line.
Control-Meta-? Editor-Help
Self documentation function. Type a single character (one of A, C, D. K, S, or 7) to
select which type of help you want.
Control-Meta-@
Mark-Sexp
Put the mark at the end of the next LISP expression.
Control-Meta-A
Beginning-Of-Defun
Backup to the beginning of the current or previous defun. Does not require matched
parentheses or a complete defun.
Control-Meta-B
Backward-Sexp
Move backward over one USP expression.
Control-Meta-C
Compile-Sexp
_ Compile the current defun. Only works. for NIL code. lbe compiled function is loaded
into the current NIL
Control-Meta-D
Down-List
Move to the inside of the next list in the buffer.
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NIL Manual 267 Glossary of Commands
Control-Meta-E
End-Of-Defun
Move to the end of the current or next defun. Does not require matched parentheses or
a complete defun.
Control-Meta-F
Forward-Sexp
Move forward over one LISP expression.
Control-Meta-H
Mark-Defun
Put point at the beginning and mark at the end of the current defun.
Control-Meta-J
Indent-New-Comment-Line
Equivalent to lOl1lrol-N Aleta-: .
Control-Meta-K Kill-Sexp
K ill the next J .lSI> expression.
Control-Meta-M Back-To-Indentation
Move the cursor to the first non white-space character in the current line.
Control-Meta-N
Forward.-L i st
Move forward over one list.
Control-Meta-O Split-Line
Break a line at the cursor and indent the second half so it starts in the same column.
Control-Meta-P
Backward-List
Move backward over one list.
Contro/-Meta-Q
Indent-Sexp
Apply tab to every line in the LISP expression fol1owing the cursor except. for the first
line.
Control-Meta-R
Reposition-Window
Try to place the beginning of the current dcfun at the top of the window without moving
the cursor. Does not require balanced parentheses.
Control-Meta-T
Transpose-Sexps
Exchange the previous and next USP expressions.
Control-Meta-U
Backward-Up-List
Move backward to the previous enclosing open parenthesis.
Control-Meta-V
Scroll-Other-Window
In two window mode scrolls the other window forward.
lines.
With an argument scrolls by
Control-Meta-W
Append-Naxt-Kill
If the next command is a kill command the previous kit1 wi11 be appended to it, even if
it would not otherwise be. Has no effect if the next command is not a kill command.
Control-Meta-X
Instant-Extended-Command
Read an extended (named) command from the keyboard and execute it. If completion
finishes the command name it will be executed instantly. without waiting for a Relurn.
Control-Meta-[
Beginning-Of-Defun
~1o\'c to the beginning of the current or previous defun.
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Glossary of Commands 268 Nil. Manual
Control-Meta-]
End-Of-Defuo
Move to the end of the current" or next dcfun.
Control-Meta- .... Delete-Indentation
Join the current line to the previous line and delete whitc space as. appropriate. Leaves
the cursor where the line scparator was, so a Lillefeed undocs the cffect of Col1lro/­
Alela-t .
Control-Meta-Rubout Backward-Kl11-Sexp
Kill the I.ISP cxpression bcfhre me cursor.
25.7.5 Control-X Commands
Control-X Control-A Toggle-Auto-Fil1-Mode
\\'ith no arg. togglcs auto fin mode. With a negativc arg. turns it off. With a positive
arg. turns it on and sets Fill Column to that number.
Control-X Control-B L i st-Buffers-
I -ists all huffers and their meljor modes.
Control-X Control-Z
Exit-Editor
Return to whoever called the editor. generally the NIL interpreter.
Control-X Control-D Directory"-Display
I.ist all versions and types of the current file. With an argument reads a pathname and
t.· , . t ••
II:'\.!) all fll\;~ WIIU,':U Illdu.:n u.
Control-X Control-F Find-File
Find-File wiH prompt for a file name and you should type it from the keyboard. If there
is a buffer for that file thcn it will be selected and be the new current buffer. Otherwise
a buffer is created for the file and the file is read in from disk if it exists therc. Find­
File is the most common way to read a file from disk. It creates a new buffer for each
file which is convenient. When Find-File creates a buffcr it uses the file name without
any extention as the buffer name. Since the name of each buffer must be unique this
doesn't work when you are editing two files which have the same name but are on
different directories, or have different extensions (file types) so Find·File will notice if you
are doing this and will ask you for a new buffer name to use.
Control-X Tab
Indent-Rigidly
With an argument shifts all lines in the region right (or left if negative) that many
columns.
Control-X Control-l Lowercase-Region
Conven all characters between point and mark to lower case.
Control-X Control-N Set-Goal-Column
COlllroi-N and COJllro/·P try to move to the goal column if there is one. With an
argument removes the goal column. Otherwise set it to the current cursor position.
Control-X Control-O Delete-Blant-Lines
Delete all blank Jines foUowingpoint, and if the current is blank delete all blank lines
before it.
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Control-X Control-P Mark-Page
Put point (.It the beginning and mark at the end of the current page.
Control-X Control-Q Set-File-Read-Only
With positive argument sets file read only.
With negative argument sets buffer read only.
With zero argument allows any access.
Control-X Control-R Visit-File
Visit-File is like Find-File except that it re-uses the current buffer. destroying its contents.
It is still safe since it will oITer to save it if any changes have been made to it.
Control-X Control-S Save-File
Sa\c-File writes the current buffer to its associated file. and changes the mode line to
indicate that the buffer and file are now idemical. (This is not done until the output is
complete. so if there is a disk error or some other error you wiJI not think it has been
StH'ed when it hasn't been.)
Control-X Control-T Transpose-lines
Exchange the cllrrent and previous lines.
Control-X Control-U Uppercase-Region
Convert all characters between point and mark to upper case.
Control-X Control-V Visit-File
Visit-File is like Find-File except that it fe-uses the current huffer. destroying its contents.
Control-X Control-W Write-File
Write-File writes the current buffer to a file. but unlike save file it will prompt you for
the file name.
Control-X Control-X Exchange-Point-And-Mark
Put point where mark is and mark where the point was.
Control-X Altmode
Evaluate the symbol n + n.
this does the right thing.
Re-Execute-Minibuffer
Alera-X and some other commands setq + appropriately so
Control-X #
Change-Font-Region
Sets the font number of the region to the argument. Good for Bolio at least
Control-X (
Start-Kbd-Macro
Begins defining a keyboard macro.
Control-X 1
One-Window
Make the current window fill the entire screen and discard all other windows.
Control-X 2
Two-Windows
Split the current window into two windows. Can create any number of windows until
they get two small.
Control-X 3
View-In-Other-Window
Split the current window into two windows but stay in the top half ..
Control-X 4
Visit-In-Other-Window
Combines Find-File and two window mode. Asks for a file to find. then displays it in a
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Glossary of Commands 270 Nil. Manual
new second window.
Control-X;
Set-Comment-Column
Sets the comment column to the current cursor column. Comment commands try to start
comments in the comment column.
Control-X =
What-Cursor-Position
Shows the X and Y coordinates of the cursor on the screen. the current character and
how far through the buffer you are.
Control-X A
Append-lo-Buffer
Adds the text of region to the end of another buffer.
Control-X B
Select-Buffer
Asks for a buffer name and creates or selects CI buffer of that name.
Control-X F
Set Fill Column
Sets the fin column to be the argument. if given. or else the current cursor position.
Control-X G
Get-Q-Reg
Asks for the name of a LISP variable and tries to interpret its value as. text to inscrt into
the buffer.
Control-X H
Mark-Whole-Buffer
Put point at the beginning of the buffer and mark at the end.
Control-X K
Kill-Buffer
R~:trl" :t h~lff~r n~rne'~nd km~ th~! buffer.
Control-X l
Count-lines-Page
Prints the number of lines in the current page in the mode area.
Control-X 0
Selects the next window.
Other-Window
Control-X T
Transpose-Regions
Transposes two regions defined by point and the last three marks.
Control-X X
Put-Q-Reg
Asks for a lisp variable and saves the text in the current region there. Designed to be
undone with Gct-Q-Reg (Contro/-X G).
Control-X [
Previous-Page
Move point to the previous page boundary.
Control-X]
Next-Page
Move point to the next page boundary.
Control-X Rubout Backward-Kill-Sentence
Kills text to the previous end of sentence.
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Nil. Manual 271 Glossary of Commands
25.7.6 Meta-X Commands
Apropos
Scarches the documentation for a string and prints all paragraphs which contain the string.
Auto-Fill-Mode
Toggle auto fill mode. With an explicit argument. turn it on if positive. and off if
negative. I forget what 0 does. Unfortunately this docs not change the mode line. It will
in thc next vcrsion.
Bolio-Mode
Bolio mode is huilt on Text mode. hut has features from Lisp mode. In particular Alcla·.
docs a Find Function and the parenthesis balancing hack is turned on. Comments are
Bolio comments. Also. ('ollfro/·,Hcta·digit and C0I11ro/·AlcIO·* insert a Co1l1rol·F followed
hy themselves. as font switching commands.
Comment-Region
Adds comments to the beginning of each line between point and mark. Can be undone
with :\IcIO·X Ullcommel11·Region. Won't work for languages with a comment terminator (l
think).
Compile
Compiles the file associated with the current buffer. With a pathname argumcnt compiles
that file instead. Asks if you want the file loaded when done.
Copy-Made-Line
Copy the first non·blank line of the last buffer selected to the first line of this buffer. An
argument is the name of a buffer to use instead.
Delete-File
Read~ a file name and deletes it. Asks for confinnation.
Describe
Reads a command from the keyboard and searches for documentation on it.
Describe-Char-Syntax
Rcads a character and lists its editor syntax. For nonnal characters just type the character
and Return. For special chractcrs you must type its symbolic name in accordance with
the currcnt readtable.
Evaluate
Reads and evaluatcs one NIL fonn. Prints the value in the mode area. Passall mode is
turned off during evaluation for safety.
Fundamental-Mode
Scts the major mode for the current buffer to Fundamental.
Help-Meta-X-Commands
Lists the AI ela· X commands. This will probably go away and be subsumed under some
more powerful help function.
Kill-local-Variable
Removes the currcnt buffer's local binding of a variable.
Kill-Same-Buffers
Asks for each buffcr whether to kill it or save it.
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Glossary of Commands 212 Nil. Manual
Kill-Variable
Attempts to makunbound some variable. May change or go away.
lisp-Mode
Scts the major mode of the current buffer to Lisp. Turns on the parcnthesis echo hack
and some other features.
ll-Mode
Sets the major mode of the current buffer to LL (Lisp Listener). Lisp Listener mode is
built on l.isp mode. but has the feature that a defun is evaluated and printed into the
buffer when it is finished. It acts like the top-level loop in many ways. except all input
m1d output is san~d in a buffer.' You also get to usc Tab and the other editor features
which help typing f .JSP forms.
local-Bind
Bind some variable to some value when in the current buffer. lf prompting fi)r input this
will tell you what the current vaJue is.
lSB-Mode
Makes the current major be LSH.
also parentheses.
Make-local-Variable
Like half of Local-Rind.
Very similar to Lisp mode. except that { and }. arc
Makes the variable local to tl1e current huffer .. but doesn't
change its value. Not sure if this is useful. it. is an attempt to sort of be compatible with
EMACS.
Name-KBD-Macro
If there is a keyboard macro this will allow you to name it and to put it on a key. Asks
for the key. then asks for confinnation about that.
Overwrite-Mode
This is not a major mode. It is also not finished. It is supposed to make self-inserting
characters overwrite the existing characters rather that move them over. This much works,
but there is some other hair which is unimplemented.
Query-Replace
Replace all occurances· after point of the first argument with the second argument. Asks
about each replacement. "?" will list the options in the mode area. Space does the
replacement, Rubout does not. Escape exits immediately. Period (.) makes the replacement
then exits, and Comma makes the replacemen~ then waits for a Space before continuing
(so you can see the change before moving to the next one).
Rename-Buffer
Change the name of the current buffer.
Renam.e ... Fi le
Takes two file name arguments. Renames the first to the second.
Reparse-Mode-line
Reset the m,ljor mode and all local variables from the file property list of the file
associated with the current buffer.
Replace
Replace all occurrences of the first argument with the second argument. Acts
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NIL Manual 273 Glossary of Commands
instantaneously (wen. as fast as a V AX can go) and leaves the cursor where it was. Note:
Currently the cursor is left at where the last string was replaced.
Save-A11-Fi·les
Lets you save any modified buffers. Asks about each one separately.
Set-Key
The first argument is a Key and the second is a binding. Control-X keys can be specified
like (# \Control-X # \Control-B). Keys should be specified is accordance with the current
readtable.
Set-Variable
sets a LISP \ariable to some value.
Set-Visited-Fi1ename
Changes the file name associated with the current buffer. but docs not change the buffer
or write any files.
Test-Mode
1\ major mode build on LL mode (Lisp Listener) but with passal1 turned off. Not feally
Slife why I did this. except to test the editor. since Passall is ofT in 1.1. mode when
reading and evaluating a fonn.
Text-Mode
The major mode for editing text. Also try Bolio mode.
Trace-Current-Defun
Tries to tind the name of the current defun and caU trace on it. Given and argument will
trace that function instead.
Uncomment-Region
Tries to remove comments from a region of commented code. Meant to be used with
Alela-X Comment-Region.
Underline-Region
If the tenninal supports underlining change the visible part of the region so it is
underlined. Waits for you to type a space, then reverts to the nonnal display and lets
you continue.
View-Buffer
Shows the contents of a buffer in screenfuls.
View-File
Shows the contents of a file in screenfuls. Until the NIL garbage collector works this is
much less efficient than visiting the file since all of the lines are wasted completely.
View-Kbd-Macro
Shows the sequence of characters in a keyboard macro in the mode area.
View-Mail
This is just a hack which runs View-File over the VMS mail file sy s$l og in: rna i 1 . rna i.
If it docsn'r work, don't use it
View-Variable
Prints the value of a LISP variable. Doesn't barf if the variable is not bound. 'Other than
that it is no better than Afcta-X Evaluate.
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Extending the Editor 274 NIL Manual
What-Page
Prints the current page number and ·1ine number.
Write-region
Writes the text between point and mark to a file.
supplied.
Asks for the file name if it is not
25.8 Extending the Editor
E\'en1U(Jl1y the internals of the editor wi11 he documented pretty completely. Currently the
internals arc suhjcct to change. so any ex(ention may be broken by futurc changes to tJle editor,
1-10we\·cr. ,IS any haCKer knows. ,l program does not change a1l that quickly... So one may
assume th,H most of the internals will not. change much. ttNol being documented" means that I
don't know which parts will change and which parts won't. su you pays your money ,md you
klkcs your chances.
25.8.1 Editor Functions
An editor function ;, just a NIL function in the package STEVE. Currently the name of the
function as given in th'smanual or with the Describe-Key command is the name of the NIL
function. unless thal conflicts with some other ~ll. function. (There has been some talk of adding
a consistent prefix or suffix to aU editor commands to distinguish them from other interna1 editor
r.~_
• VA
example the I.lSP fonn (steve:forward -word) will move the cursor forward one word. just like
Alela;.F would. Numeric arguments arc passed in the global variable steve:*argument •.
steve: ed1tor-b1 nd-Icey key-sequence binding &optional motir-name
key-sequence may be either a character object or a list containing two character objects. It
is evaluated. The code field of these characters should not be an ASCII control character;
use the bits field to select a control character. A list is interpreted as a two character
command using a prefix character (generally Control-X). The binding is not evaluated. It
may be a function name, an editor command macro specification or a key indirection.
Nonnally the binding is a function name to call when the key is typed. The function will
be called with no arguments.
If the binding is a character object the binding for that character object is used instead.
This is only used for binding Control·/ to Tab. so it may not be very robust
A list is used to define an editor command macro. The car of the list is a function and
the cdr. is a list of arguments. When the editor is reading the key as a command the
function is called and its values are returned as the "key" and command. This is hairy
and should not be used lightly. Look at the code for numeric arguments and bit-prefixes
to see how it can be used.
lbe mude--Ilame is used to find the binding table for that major mode. The major mode
must be declared when this is executed. The default is to usc the current major modc.
which is nonnally fundamental when not in the editor. i.e. when linking· NIL.
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NIL Manual 275 Extending the Editor
If the binding is a symbol then it is also defined as a Alcta-X command. Not sure if this
is good but thaCs the way it is right now.
steve: ed1 tor-defun-Key key-sequence name &body fonns
A cross between defun and editor-bind-key. Dcfuns name to be a no argument function
with a body of jonus and binds it to key-sequence using editor-bind -key. There is some
debate about whether to use this function or not.
A number of the editor functions take optional arguments which arc intended to make it
easier to usc them from I"II. code. Usual1y these

Extending thc Editor 276 NIL Manual
steve: make-l1 ne buffer previous Ilext&optional sIring
Returns a line in buffer between prel'ious and next containing siring. If next is nil this
will be the end of the buffer.
steve: buffer spec &key :create
spec may be a pathname. a buffer name (as a string). a buffer or an edit-cursor. The
value is either nil or a buffer. which is found or created using spec. The keyword
argument creale determines jf the buffer is created when it docs not exist already. 'lbe
default is to creatc a new buffer.
steve:po1nt 5P(,(, &key creale
l.ikc buffer except returns an edit-cursor. The argument ('reat(' controls whether a butfer
is crcated in order to build the edit-cursor. (If there is () buffer then an edit-cursor will
a1ways be returned. regardless of the value of creau. An edit-cursor must hm"c a bufl'er.)
The edit-cursor may Of may not have a window.
steve: paint-selected spec &kcy creale
l.ike point except that the edit-curSOf is selected" as the current cursor and its huffer is the
current buffer.
This last function uses primitives which are useful in their own right.
steve:select-po1nt point
Make poi11l he the current cursor and its huffcr the current huffer.
steve: select-po1nt-1n-current-w1 ndow poini
Like select-point except the window of the current cursor is stolen. This is usually the
right way tp sclect a cursor.
SonIC common operations on lines. These arc done carefully, so as to do the right thing at
the beginning and end of the buffer.
steve: line-next line
Return the line after line or nil if at the end of the buffer. This is a macro generated by
defflavor.
steve: line-previous line
Return the line before line or nil if at the beginning of the buffer.
steve:nth-next-l1ne line n
Return the line n lines after line ~ If the cnd of the buffer is reached. the last line in the
buffer is returned. If n is 0 the first argument is returned. If n is negative, moves
backward.
steve:nth-prev1ous-l1ne lille n
Like nth-next-line except moves up for positive n.
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NIL Manual 277 Extending the Editor
Some operations on bps.
:advance-pos n
Ask the bp to advance by 11 chars. Line separators count as 1 character. Bombs back to
the editor top level at beginning and end of buffer.
: move lille Il
Place the bp pointing to the nth character of line.
:get-char
Return the character that the bp points to.
:get-char-forward
Return the character that the bp points to and advance over it.
:peek-char-backward
Return the character before theme that the bp points to.
:get-char-backward
Return the character hefore the one that the bp points to hackup to point to it.
Note the unpleasant asymmetry of names. However. none of these can be interpreted as standard
stream messages.
25.8.3 Other Functions and Conventions
Editor errors.
steve:save-all-f11es
This is the Aleta-A' Sal'e-All-Files function. It may be called from outside the editor if the
editor is broken, and may be able to save your buffers.
steve: ed-lose [omlal-string &restv [onnat-args
Abort any operation immediately. Print the Jonnat-string and ring the bell. then return to
the editor top-level. The [orowt-string is printed in the mode area. Passal1 mode is
turned off while aborting to the top level, so if a bug causes a repetitive error you can
escape by typing Conlrol-C at the right instant. Keep trying, it works, but it may take a
few tries.
steve: ed-warn [onnat-string &restv [ormat-args
Like ed -lose except the ben is not rung. In general ed -lose is used when the editor
detects an error. and ed -warn is used for predictable events, like the Colllro/-G abort out
of a command reader. I fee1 that if the user has already done something to cause an
abort h('/she will not want to hear how upset the editor is. The bell is to bring attention
to something unexpected.
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1':Xlcnding thc Editor 278 Nil. Manual
steve: ed-w8rn1 ng jiJnnl1l-s/ring &restv jbnllal-args
Print ji)rmal-slrillg in the mode area, and continue. Docs not cause an exit to the editor
top-level. but continues any operation in progress.
steve: wi th- no- pas s811 &body fom7s
Execute fonns with the terminal not in passall mode. Sets up an unwind-protect form so
an abort is o.k.
steve: *ed1tor-dev1ce-mode*
Variable
The editor sets the tenninal to passall mode only if this variable is t. If you write an
editor function which turns passall 011' and on yuu should always usc the fimn:
(send terminal-io :set-device-mode
:passall steve:*editor-device-mode*)
Arguments.
steve:argument?
Use the fonn (steve:argument?) to determine if any numeric a 'gument was given.
steve:c-u-only?
Returns t if the argument was Colllroi-U with no number.
steve:rea1-arg-sup?
(and (steve:argumentl) (not (steve:c-u-only71»)
But more efficient in 'code and runtime.
steve: buffer-beg1 n1 &optional bp
Test whether bp (or the current cursor) is at the very beginning of the buffer.
steve: buffer-end? &optional bp
Similar; test for the end of the buffer.
steve: f1 rst-l1 n8? &optional bp
Returns t if the bp is anywhere in the first line of its buffer.
steve: 1 ast-l1 n8? &optional bp
Analogous.
steve: not-buffer-begin &optional bp
steve: not-buffer-ef)d &optional bp
steve: not-f1rst-l1 ne &optional bp
steve: not-18st-11 ne &optional bp
Return to the editor top level if the bp fails the given test. Otherwise do nothing.
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NIl. Manual 279 Extending the Editor
Redisplay
steve:make-screen-1mage
This is poorly named. It used to be different. Now it is the redisplay entire and
complete. Just call it and the screen will be redisplayed. (If a character has been typed it
will exit immediately.)
steve:setup-mode-area
Generate and print a current mode line.
Some functions use the upper area of the screen to print things. The redisplay must he
told that tJlis has happened. This is handled by using several special tlmclions to position
tJ1e cursor and to do terpri. It is possihle that this will he changed and that there will be
a special stream which keeps track of such things. I was sick of defining special purpose
streams when I got to this.
steve:overwrite-start
Begin to overwrite the display. If there has b~en some overwriting of the screen since the
last redisplay s141rt after it. Otherwise start at the top.
steve:overwr1te-home
Start at the top always.
steve:overwrite-terpr1
Move the cursor to the next overwrite line. 'r11is will do .more* processing as needed.
steve:overwrite-done
Always call this when finished with an overwrite display. This makes overwrite-start begin
in the right place if called before a redisplay.
Reading from the tenninal.
steve :mx-prompter function jonnal-string &restv fonnat·args
Prompts in the mode area using jonnat-slring and jonnat-args, then reads from the
tenninal using junction. Handles C011lrol-G and has some additional internal hair which
allows completing functions to be defined. May be modified to handle ? as a help key
somehow.
steve:read-f11e-name
Can only be used as an argument to mx-prompter. Reads a file name and returns it as
a string. Some day this will do completion.
steve:read-buffer-name
Only for usc as an argument to mx -prompter. Will do buffer name completion and
respond to? Example:
steve:(mx-prompter ,'read-burfer-name "Foo(-a): " faa)
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The Patch Facility 280 NIL Manual
26. l"he Patch Facility
The patch facility provides a means by which a program (whatever that might mean) may be
incrementally updated: it essentially a bookkeeping operation. and is primarily designed for
providing the updates necessary for a dumped-out system. In the context of the patch facilIty.
such a program unit is called a patchable system: usc of thc term system in this context means
the same thing, but may not in other contexts. (NlI. has no more sophisticated system-building
tools currently. although it cenainly has whatever primitives might be needed.)
The design of the !\Il. patch facility is originally derived from the uSP M:\CIII~F I.ISP patch
fllcility [121. That was first implemented from scrcttch in \1:\('1 lSi>. and some time later the
\1.\( 'lISP \·ersinn was copied and modified to he more appropriate for ;\11. This is noted because
there arc \ariou~ design flaws and misfcatures of the filciJity. which arc inherited and are due in
part to the application of the techniques used to a different programming environment. A future
release should have a redesigned facility which will correct these things.
Palchah1c systems have both m(~;or and millor .version numbers. The major ve/sinn number
corresponds to a complete new system generation. like when a :\11 maintainer (one of' the authors)
loads lip a new :'\11. having incorporatcd any fixes into the source files and rccompiled any files
which needed it. '1l1e minor version number is incremented whenever an update is made. The
updates are maintained on disk: each one corresponds to a particular file (a patch file) which
implements the fix (usually. some function and variable definitions the same as in a newer version
of some source file). A patch directory is maintained for each major version number: it
ClIUtll\'·ICtic~ (ami JC~I iiJc!'l) iilc Pi.lll.:itc~ fur ciu.:h minor vcr~ion numher. Finaiiy. each palchabie
system has a palch system definitiol1 Jife. which primarily provides all kinds of default attributes
about the system. which include the current version number and the location of the otlier files in
the filesystem (thus the only place a pathname need ordinarily be specified to the patch facility is
when pointing at the patch system definition file to define the patch system originally).
A typical cycle of usage for the authors might thus look like this. We have a freshly-made
NIL. say version 175 (the Release 0 version). As bugs are found. they are accumulated into patch
files. One person might accumulate several fixes over the course of a day into a single patch file.
This might then be the update which makes Lisp 175.0 become Lisp 175.1. Exportation of the
patch directory and the patch files for Lisp 175 to other sites will then allow them to be loaded
by other dumped-out NILs of Lisp version 175. Eventually. one of us will decide that the
changes are too far-reaching or too numerous. and decide to go on to another system version.
This normally involves ensuring that aU updated sources are recompiled, loading up a new NIL,
and telling the patch system we want a new major version number. Note that the last is
independent. conceptually, from loading up a new NIL: it is an operation which says that what
we have on disk is a new version. A conceptual bug in the distributed NIL is the case with which
one may load up a NIL and increment the version number. Unless one is actually modifying the
files which get loaded. onc's site should remain at NIL version 175. If it does not. then a bug
report referring to the NIL version is meaningless to us.
At the end of section 26.4. page 285. is a description of a more common usage of the patch
system. where it is used for a system which is /luI dumped out.
MC:NII.MAN:PATCH 25
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. . ,
0~j~}l~~

Nil. Manual 281 User Functions
26.1 User Functions
load - pa tchas &rest poorly-desiglled-keywords
Loads patches for the specified (or all) systems. This takes keyword arguments in a nonstandard
fashion. although that is expected to be changed incompatibly in the future. All
of them except for :systems take 110 arguments. They are:
:systems list-afsystems
Load patches for the specified list of patch systems. rather than all those currently
defined.
:verbose
Be verbose. (Verhosity is forced when there is interaction. of course.) This is the
detlUll.
:silent
Don't be verbose.
:noselective
Don't be interactive. just load the patches. The d~',:ault is to query the user on
each patch,
:selective
Query for loading of each patch, This is the default. Note that one may answer
P instead of Y or N to the query: this means proceed. which will cause all
succeeding patches to be loaded non-interactively. load-patches is (supposed to
be) clever to force verbose typeout when it is going to ask. and inhibit it again if
:silent was specified and the loading was proceeded.
The standard l'IL default init file does a
(load-patches :noselective)
to load patches without querying. but verbosely (so that you see what might be taking it
a while during startup).
The fol1owing two functions, if given no arguments, print infonnation about all defined
systems: otherwise, about the systems given as arguments.
pr 1 nt-sys tam-mod 1 f1 cat ions & rest systems
This prints infonnation about the systems as they exist in core. For each system. it lists
its (current) status. and lists the minor version numbers that have been loaded, and their
dcscrip tions.
pr1 nt-systam-h1 story &rest systems
This reads the patch directory for the named systems off of disk. and displays the
infonnation: al1 patches and their descriptions are listed (whether or not they have been
loaded), status changes (the system status may change with a particular minor version
number) are noted, and the "in-core" status with respect to all of this is shown.
Note that although the patch directory is read from disk. the patch system must be
defined in-core in order for this to know where to look for the patch directory.
MC:NII.MAN;PATCH 25
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Patch System I n formation 282 Nil. Manual
26.2 Patch System Information
s1 :system-vers1on-1nfo &optional briefp
Returns a string describing .the versions and statuses of the patch systems defined. If
briefp is specified and not nil, then the status infonnation will be abbreviated, some
rinsignificant") systems will not be shown, and the name of the primary system rLisp")
will be omitted (it always comes ·first).
s1 :get-system-vers1on &optional system
Returns multiple valucs describing the current version of thcspecified patch system:
• the major version number.
• the minor version number,
• and the system status keyword.
By some special strange dispensation. if system is not defined as a patch system, nil is
returned as each of the values.
s1 :get-system-vers1on-l1st syslem
This is a vestigial r~mnant of Maclisp implementation. Equivalent to
( m u 1 tip 1 e - val u e - 1 i s t (s i : get - s y s t e In" V e r S ion S)'SI em) )
(In ~1:\n IS£>, the multiple-\'alue support code docs not normany reside in core. and code
which runs interpreted and needs to examine system version infonnation (for instance
when loading up a system) might not want to force it to be loaded.)
s1! pr1nt.-hAr~1 tt &optional 'Otrp(lIn In()Jr.nu!~r:if-t:f)"f'?
This is what prints the startup message. If look-oul-ofcore? is not nil. then si:printherald
reads the patch directories off' of disk so that it can show what the current versions
and statuses are (what you would get if you do load-patches). With a non-null look-oUIof
core? si:prilll-heraid effectively docs a (si:update-system-statuses nil) (q.v.).
s1: update-system-status8s? system-list
Looks on disk and corrects (if necessary) the in-core status information for each of the
systems in system-lisl, or all defined patch systems if that is nil. The reason for this is
that it is possible for the status of a system to change on disk (a particular patch might
be deemed to be broken, or the system might be deemed to be no longer experimental,
for instance). This is done implicitly by load-patches. and by si:print-herald with a
non-null second ar$ument.
26.3 Adding Patches
For th~ fonowing set of functions. a default systcm/minor-version-numbcr pair is maintained.
from which system-name and mil1or-version-number are defaulted. The system name originally
defaults to lisp, which is the name of the NIL patchable system. (This should be changed.)
s;;add-patch creates a new minor version number, allocates it in the patch directory. and sets
this in-core default patch version to that. 111cn one can (for instance) do (si:compile.. loadpatch)
to test that patch. If the function docs not know which minor version numher to deal
with, then it will cyclc thruugh aU of thcm, from the "most likely" one first. asking. One way to
filrce this behavior is to specify a system but not a minor version number to one of these
functions.
MC:NII.MAN:PATCH 25
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NIL Manual 283 Adding Patches
s 1 : add - pa tch &optional system-name descriptiol1 &rest options
This allocates a new minor version number for the patchablc system s),slell1-llalllc. with a
description of description and environment options of options (sec the :environmentoptions
keyword to the si:initialize-patch-system function. on page 285). It then calls
si:re-edlt-patch. below.
s1: re-ed1 t-patch &optional system-name millor-version-number
Creates a patch file for the appropriate file (if necessary). and calls the built-in editor on
it.
s i : comp 118 - pa tch &optional !l),SICI11-IIc1I11C mill"r- version-numbcr
Compiles U1C specified patch. This routine relllrns several val lies: the first of which is the
path name of U1C compiled file. so that it may he loaded.
s 1 : comp 118-1 oad - pa tch &optionaJ s),stem-name minor-vcrsion-number
Compiles and loads the specified patch.
s 1 : fin 1 s h - pa tch &optional system-name mil1or-versioll-llumber
"Completes" the specified patch: that is. marks it as finished. I f a patch is not
"finished". then load-patches wiJl not load it (nor any succeeding patches).
s 1 : abort - pa tch &optional system-name millor-version-number
Flushes (aborts) the specified patch. Any patch files arc not deleted. hO\l,'e\,er: you should
consider doing that manually. If the minor version numher was the highest in lise, it wi1l
be rellsed. in which case a later si:add-patch will usc the existing text file to start.
Otherwise, there will be a missing minor version number, which is ok.
s1: set-patch-env1ronment system millor-version-l1umber &rest options
In case you forgot with add-patches. this sets the option environment to opticms. Note
it docs not update the file attribute list in the' source file of the patch ! You must do that
manually.
s1: set-system-status system status &optional major-version minor-version
Note that "this takes weirder than nonnal arguments. This sets the status of the specified
version of system to be status. It is willing to modify the status list of major versions
differing from that defined in the current environment. (Not to say that that would not
be equally useful for some of the other functions ... )
The typical use of this is to set either the current or the 0 minor version number of the
current major version of some system to either :released or :broken, with the current
status being :experimental (the default when a new major version number is made). Or.
to change the status of an antiquated system from :released to :obsolete.
MC:NIl.MAN:PATCH 25
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Defining Patch Systems 284 NIL Manual
26.4 Defining Patch Systems
s1: new-patch-system system-name pat/moille &optional (do-what :increment-alld-define)
s1: 1n1t1al1ze-patch-system system-name palhllame &key :initial-version
:patch - directory :patch - file :compilation - function :editing - function
:insignificant :default-directory :default-device :nodefault
:environment-options
:nodefautt
If not nil. then si:initialize-patch-system will read in an eXlsttng version of the
patch system definition file from pelflmam (appropriately dd:lllltcu) (0 provide
de~lllils for those options not specified. Otherwise. hopefully appropriate default
defaults arc used.
:initial-version
May be used to specify the version to he uscd. Thiswitl be written into the
patch system definition file as the CUrrl'1I1 version. which means that calling
si:new-patch-system with the (typiccdl) :increment-and-define keyword will
increment it first.
:patch -directory
A fonnat string which should take one argument. which is . the major system
version. to construct the patch directory pathnamc for that major system version.
·n~tr.h -fil~
r·· -
A format string which should take two arguments. the major and minor system
versions (in tllat order). to construct the patch file patllname for thepatchs of
those versions. Alternately. it may be a list of two such fonnat strings: the first
will be used as the source file pathname. the second for the \'asl fiJ~. (This may
be used to split the stuff across directories or even structures, for instance if the
sources are kept in a different place because of lack of disk space. or are simply
not kept somewhere on some particular machine.)
:compi lation - function
The function caUedby compile-patch etc. By default compile-file (page 244) is
used. This should be a. symbol. not a closure or compiled-function object. The
function wiH be given a first argument of the input pathname. and other
kcyworded argumenl~
of :output-file and :set-default-pathname (which will be
nil so as to not modify pathname defaultS). That is,
( 1 sbe 1 illpul-parhname
: output-fi 1 e output-pathname
:set-default-pathname nil)
:editing- function
The editing function which should be used to edit a patch file. It is cal1ed with a
single argument. the patch file path name. The default function simply returns the
list of "now" "edit" and the pathname 9 which is then returned by si:add-patch
or si:re-edit-patch.
:insignificant
If not nil. then si:system-version-info will not show this system when in brief
MC:NII.MAN:PATCH 25
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NIL Manual
285 I )cflning Patch Systems
mode.
:default-directory
:default-device
These are used to construct the default pathnames used for the :patch-directory
and :patch-file options, when they are not supplied. They are 1101 used in
defaulting (although they probably should be). The default-defaults for these are
taken from palhllame. and if absent from that. the directory name defaults to
system-name. These options are significantly less useful in 'II. than they were in
the ~1ACI .IS}> version of this code ...
:environ ment - options
This and some of the code involved is partially but not totally archaic: it predates
:\11. file attrihute lists. and was put in to compensate for their ahsence. The code
in Release 0 still performs redundant bindings of the in\ohed attributes.
However. the data in this option list is used to also initialize the textual file
property list when si:add-patch initializes the 'patch file. Because of the
kludginess of this. only a few options are supported. although it is extensible if
need be (see the code). The options currently handled are
:package
The package name (default is "SYSTEM-INTERNALS", which is probably
a poor choice)
:input-radix
The input iadix (default i5 dedman.
LSB, which has been distributed with NIL, is a patchablc system also. However, the nonnal
~IL environment does not have LSB loaded by default. There is a file which can be loaded which
wi1110ad up all of the parts of LSB. (It is NIL$DISK:[LSB]LOAD.LSP. if you have ISB online.)
Esscntially, it sets up the Isb package and loads up all of the component files of lSB and
performs whatever initializations are needed, and then does
(si:new-patch-system
"LSB" "NIL$DISK:[LSB.PATCH]SYSOEF"
:define)
(load-patches :noselective)
The file N 1 L$D ISK : [LSB . PATCH ]SYSDE F • PSD was created with the si:initialize-patch-system
function. Once that has been created, this refcrence to it in the ISB loadup file is the only
pathname reference necessary; all others are contained in that file.
With the LSB patchable system, the files which are loaded by the loadup file are not nonnally
modified except via patches. However, at strategic points. like when many files are being changed
at once, or incompatible changes are being made. or the patches become numerous. then all of
the files are changed (for instance, recompiled) at once, and the maintainer manually increments
the version number of the LSD patchable system by doing
(si:new-patch-system 'lsb "nil$disk:[lsb.patch]sysdef"
:increment)
which increments the on-disk version number. Then. when someone loads the loadllp file. they
get the new files. the new major version number, and (until new patches gel made) no patches
loaded.
MC:NII.MAN:PATC1-I25
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Defining Patch Systems 286
M~intaining the system in this way also result'i in a shorter turnaround time for testing out
small fixes. and getting them "installed"; larger source files do not need to be rccompiled.
~lC:~II.~1AN:PATCH 25
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NIL Manual 287 Talking to NIL
27. Talking to NIL
27.1 Startup
'Inc first thing ~IL docs when it starts up is to attempt to figure out what kind of tenninal
you arc using. The way NIL figures out how to talk to a particular tenninal is that it uses
"tenninal capahilities" database (a C~IX lenncap database). "Ibe VMS logical name term is used to
name the tenninal type: ~II ignores VMS tenninaI infonnation. If no such logical name is
defined. then ~Il will assume tJle tenninaI is a simpleminded printing terminal. and prompt you
for a tcnninaI name.
The terminal names which arc both supported and known to work fairly wen arc
vt52
Standard DEC VTS2.
c100
Human De~:gned System's concept-"IOO. This will probably work for their Concept-l08
also.
aaa
Ann Arbor Ambassador
vt100
DlT vt100. Obviously you should make sure your vt100 is in ANSI mode. Also. autolinewrap
should be disabled.
In OCL. one m igh t say
$ define term "cIOO"
if one was on a concept-H)(). Or. if your tenninal varied. you might put in your log in. c om file
$ inquir term "Terminal type (in doublequotes. default vt52)"
$ if term _eqs. "" then term := "vt52"
$ define term "-'term'"
which would prompt for the tennina] type to assign to the term logical name, defaulting it to
whatever was convenient.
When NIL starts up, it loads your illit file if it exists. This would be a file on your login (not
default) directory named NIL ~ I N I. (lnit file conventions are discussed on page 200.) Then it
enters its standard read-eval-print loop.
~1C:NII.M;\N:TAI.K 16
23-DEC-83

"I'hc Toplevcl J .(lOP 288 NIL Manual
27.2 The Toplevel Loop
•
••
•••
Variable
The value of this is the last thing the top)cvel (or brcakJevcl) loop evaluated (and
presumably printcd).
The previous value of •.
The previolls "alue of ••.
Variable
Variable
+
Variable
The \'alue of this is the last thing rcad in by the top)evcl (ur breakleve1) loop.
++
+++
Previous values.
Variable
Variable
\\
Variable
This has as its value the lteClor of values returned from the last thing evaluated' by the
toplc\ cl (or brcaklcyel) loop. That is. its first (number 0) e)cment will be the value of •.
This variable is also used by the dcbuggcr the way • is by the toplcvel loop. but that
will bc changcd eventually.
If an evaluation error occurs and you abon back to toplevcl, then the valuc of the • variables
docs not get cycled. but the + variables do: thus. + is the fonn which got the error, but • is
still the last thing returned by toplcycl evaluation. C0\1\10\ LISP intends to change this. (What
NIL docs is compatible with MACLISP.)
27.3 Entering and Exiting NIL
Typing the character control-Y normally exits from NIl. The same command which started
the NIL initially may then be used to resume it. The NIL can be resumed in other ways too. For
instance, if nil was thc command used to stan the nil,
nil
will resume the existing NJL,
nil/kill
will kill the NIL, and
n i 11 pro c e e d will resume the NIL, but not allow it to type out. and will leave you in the
command interpreter. If the Nil. attempts to type out (or. in fact, calls any of
the following functions). it will wait until it is explicitly resumed.
If SIL is reading input from the tenninal, the input processor command for "meta"alunode'"
which may be typed as the character sequcncc CUllIro!- \ a!/mode, will return control to the
command interpreter. When the NIL is resumed. it will automatically redisplay the typein it is
accumulating.
MC:NII.MAN:TALK 16
23-DEC-83

-., il"AIIl'ii!il':!I' '. '~-~--' -' 7r' '''r ,'" ' :"°11' E'"
N II. Manual 289 Entering and Exiting NIL
Sc\'e'ral functions are provided for returning from Nil to the \'\1S command language
interpreter (ell) in a more programmable fashion. In all of the t()lIowing functions where a string
is involved with passing control back to the cu. the string may have a maximum length of 256
characters. This is checked for by NIL
val ret &optional command-line
(valret) returns control to the CLI. The NIL is suspended until later resumed.
(val ret cOll1l11tllJti-lin(') returns to the n.I (suspending the ~II,).
commalld-lin(' to be interpreted as a command line by the CI.J.
and additionally causes
quit
The passlIlI terminal mode is cleared, and restored when the 'II is reslImed.
a string ~lrglll1lcnt works hy calling the \'\tS lib$do_command library routine.
(quit) exits the NIL, causing it to be killed.
valret with
Currently. (quit SIring) kiHs the !\Ii. and causes Siring to be printed instead of "N II.
Terminated": howe\ er this will probably be changed so that SIring will be interpreted (IS a
command line. as with valret.
Passall mode is cleared on exit.
\\'hen the ~II. is terminated. there is a noticeable pause before the command language
interpreter returns. This is due to the controlling program (R'II.. nlllning in the ell)
waiting t()r the process to actually go away. V\fS image rundown wkes a noticeable time.
and if one were to not wait after requesting process deletion. starting up a NIL of the
same name immediately could cause the new R~IL to be confused. (This is the same as
happens when nil/I< i 11 is used in the cu.)
ex 1 t - and - run - program (pathname)
Control is returned from NIL to the CLI. and the program image found in pathname is
then run. The l'IL will have been suspended. ~IL applies no defaulting to pathname,
however. the command interpreter will supply a default file type of exe and will default
the device and directory to the RMS default
PassaJl mode is cleared on exit. eXit-and-run-program works by having the RNIL
program caIl the lib$run_program library routine.
proceed-nil &optional SIring
Control is returned from the NIL to the CLI. However. the NIL is resumed. so will
continue running "without the tenninal". If a SIring is supplied, then that is printed (as
with quit). Similarly (as· with quit). the interpretation of Siring should probably be
changed to be a command line for the eLI to execute.
MC:NII.MAN:TALK 16
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VMS 290 Nil. Manual
27.4 VMS
VMS usurps control-Y as interrupt-to-superior. Resuming your NIL gives it a tty-return
interrupt which makes it frob the cursor so that it knows where the cursor is. (This is why it
goes to the bottom of the screen on a display tty.)
Other tenninal intermpts are aU perfonned by dispatching from c(}ntrol-C~ after the control-C
is typed another character is read. ("?" lists options.) The contro]-C processing is perfunncd by
l.isp code. This means that control-C win not be processed if interrllpt~ arc severc1yinhibited.
The ~II system hy special dispensation will enter the VMS debugger if multiple control.;Cs are
typed and arc hC'ing ignored: so if something large and uninterruptih1c is happening. like creating
it veClOr with a mjllion clements. or something not so large but your system is slow. you might
throw the :"11 out to the V\IS debugger.
It is highly unlikely that Nil. will enter the V~fS debugger unless explicitly told to do so.
Here arc two \,\15 debugger commands that are useful for returning back to the wurld. Say
call debug .
and the lisp dehugger will be entered. (Exiting $oftly from the Lisp dcbug;:i:·'r with "q••
will
return to the \'\IS debugger. One may also perfonn a non-local exit from the l.isp debugger with
control-G or X.) One can also just
call quit
frum the V~fS· debugger. which docs a throw just like contro)-G docs from the control-C prompt.
'.11(\ only prnhll'm witl1 ~H thi~ is. tJ,:lt ifth~ 'A1S d~bugg~r gets dynamka1!y laadt'd inta t'1c
11\11. some part of it will end up where ~IL thinks it is putting its heap (Le.. where it is anocating
the memory to use for consing). and U1C ~Il.. will die shortly thereafter.
s1:11sp-debugger-on-except1ons
Vanabk
If non-null, then error conditions and faults will trap to the LISP error handler rather than
bombing out to the \~S debugger. This can happen from memory access violation errors,
floating overflow and underflow, integer divide by zero, ctc.; in general, any such error.
For instance, a reserved operand fault might occur if a variable-field byte instruction was
given a bad size.
If the lisp debugger is used from some exceptional condition, remember that the stack may
not be in a nice-looking state, so examination of what the debugger thinks are local variables near
the top may resull in more trouble. Note also that the Lisp code is not run at AST level, but
rather as a continuation of the condition: returning a value from the debugger returns that value
from the most recent VAX procedure call, which is probably the function within which the error
was signalled. Also. the USP code which handles such errors binds si:lisp-debugger-on"
exceptions to nil when it is running: examination of non·USP data by the debugger from such
an error as if it were usp data might cause a memory protection violation, and blowout to the
VMS debugger.
Note also the set-privileges and get-privileges functions (page 233). which can be used to
set or get the privileges the 1"11. process has enahled.
~lC:NILM"N:T"LK 16
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N II. Manual 291
I nSl41llation
27.5 Instalhltion
There are 4 parts to installing VAX - NIL at your site.
J
Restoration of the nil directory hierarchy from the backup tape.
2 Definition of the required logical names and symbols.
3 Invoking the LISP dynamic Iinkcr.
4 Handling System and User considerati

I nsutllation 292
NIL Mctllual
example: To go from \,~1S 3.0 to VMS 3.4 you may have to do the following:
$ BLISS/LIB NILLIB:NIlLIB
$ SET OEF [NIl.FOO]
$ BLISS RNIl
$ @RNILLINK
$ NLINK
$ LISPLINK
[Step 4)
See the file NIL$OISK:[NIL.COM]NILINSTAL.COM. which can be mo,'ed (perhaps edited first)
to SY$$MANAGE R. Then add this to SYSTARTUP. COM: .
$@SYS$MANAGER:NILINSTAl
Then lIsers who \\ ~lIll to usc \11 must h~lve executed in their login files:
$@NIL$DISK:[NIL.COM]USYMS
This will set up the the standard way of calling Nil .•
$ NIL
Which will run r\JL as a subprocess. 'tV or (valret) will exit the subprocess: to resume, type:
$ NIL
or to kill the subprocess:
$ NIL/KILL ! from OCl
(QUIT)
from IISP
The directory [NIL.SITE1 has two files of interest: [NIL.SITE]SITEPARAMS which jf it exists
in compiled fonn will be loaded right before the LISPLINK saves thcvinual memory image.
And [NII..SITEjDEFAULTJNI. which is loaded at "re-startup" time if the user docs not have a
SYS$I.OGIN:NILINI file. After N1L is created on your system then you should edit
SITEPARAMS and compile it. The information is noncritical however.
Upon startup NIL will look for the logical-name ftTERM" to detcnnine the type of terminal it
is connected to. For example:
$ Define TERM "vt100"
Presently it docs an its own cursor positioning using the data in the file NILSTERMCAP. If the
logical name "TERM" is not defined then NIL will prompt the user for the info upon stanup.
[Optional Verification 1
In NIL do:
(LOAD "NIlSDISK:[NIl.VERIFY)VERIFY")
(VERIFY "TEST")
Then sit back and watch the little demonstration. No. we do not have program verification
technology to the point where this gives a proof of correctness for the NIL. However ... , then run
$ DIFFERENCES NIlSOISK:[NIL.VERIFY]TEST.LIS
(What if FaiJure?j
If you ran out of disk space in step 1, then we can suggest that you somehow make more space
temporarily. (e.g. backup and delete fites), and then prune down to the minimum given in
NII.S])ISK:(NIL.PORT]MINIPORT.COM when step 3 is completed.
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NIL Manual 293 How the Nil. Control Works
Step 2 couldn't fail. as all it does is define logical names and symbols.
Step 3 could fail if various system generation parameters and account quotas are not set high
enough. Many sites will fail here, as the default VIRTUALPAGECNT of 8 thousand pages is not
sufficient. (Although it is sufficient to do LX BNIL which does not load the compiler): 16
thousand pages is enough to get started in lisp programming. Other things to look out for are
insufficient pagefi1c and per-account pagefile quota.
Default account parameters as supplied by DEC have found to be sufficient under VMS 3.0.
but some sites have been found to severly restrict parameters. which has proved to be extremely
frustrating. at that suhset of those sites where the local expertise for debugging prohlems caused by
Stich restrictions is insufficient.
It is possihle to nll1 NIL on a V AX-11/750 with a single RK07 disk. (a mere 27 megabytes!)
as we do here at MIT. However. it is not possihle to link a NIL on such a tig.ht system. Ideal
system environments have been found on sites config.ured to rlln large databases efficiently.
In step 4. note that the running NIL image is mostly pure. sharable. code and data, so there
is a big performance payotf in proper insWllation and SYSG EN tuning on a multi-NIL -user
system. If LISPl.lNK works. but NIL docs not, then it may be due to insufficient global sections
and pages.
rOther Options]
If vou want to be able to use the VMS debugger on the nmning lisp imrlgf' rhf'n ('1(C'('ut(' th('
following:
$RUN [NIL.HACKS]SETDEBUG
Giving NIL$DISK:[NIL.EXF]LISP.EXE: as the filename, and answering Y to the question. With
this setting NIL will start up in the VMS debugger. and you must type GO(CR) to actually start
it.
27.6 How the NIL Control Works
This section notes how some of the above stuff works, for the interest of VMS haCKers, or
those wishing to extend the above functionality.
Program control of NIL under VMS works in a fairly strang~ way (or at least so it will appear
to someone used to operating systems in which there is more explicit job/terminal association and
more "monitor" control of inferior processes). This is a function of VMSS lack of a concept of a
job "having control of the terminal", and the fact that the N1L process does not contain a
command language interpreter in its image: the spawn and at tach commands are only
implemented by conventions applied by the CLI.
The command nil typically invokes the RNIL program. This is an image which runs within
the CI I process, and "controls" the !'Il., which is kept in a separate process. The nil command
implicitly supplies lots of arguments to RNIL. one of which is the job name of the NIL process.
R'II ~ ill create one if there is none, or will do something else to it (like resuming it) depending
on additional arguments given (like ni l/proceed or ni 11k ill). RNll communicates to the
NIL process with mailboxes. When the ~Il is resumed. the RNll. attempts to read from one,
MC:NILMAN:TALK 16
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How the NIL Control Works 294 NIL Manual
walling. It returns either when it succeeds in reading a mesSt1ge (as happens with valret). or if it
is abnormally exited (41S with typing contro)-V).
VMS in its current state does not have the concept of a particular process having "contro'" of
the terminal it shares with the rest of the process trec. NIL handles this by having a number of
event and stale flags which ten it whether or not it is allowed to read from or write to the
tenninal. When a Nil. is exited. the R~II. program clears those flags: when it is resumed. they
arc turned back on again.
Exiting from ~II with contfol-Y works in a particularly strange fashion. The VMS (enninal
dri\er will give it control- Y AST (0 any process whi(:h has enahled it with no conceptualization
of what program is "in comrol or the tenninal. The control-Y is handled by the CI.I. which
then commences image nmdown of the R~IJ. program. R~1I has (In exit handler which then sets
the tenllinaI input and output enabled flags off in the!':11 process. (As a special case. it may also
exit similarly if the ~II. is terminated somc other way. perhaps by ex it to the "'1S debugger in
thc NIL process. It recognizes the mailbox message for this. and prints "NIL Terminated".)
'
Control-C has a similar control problem. When a controJ-C is typed on the termina1. the
terminal drivcr nms t11C AS.,. routincs for all processes which have enahled thclll. (Multiply. if a
process has cnah1cd more than one.) In the current implementation. thc ~II. process en~lhJes the
conlrol-C AST. \Vhen the AST routine is run. it attempts to detennine if it should be the
rccipicl1l of that interrupt. by checking to see if it "has control of the tenninal" (i.e.. the
terminaHnput-enabled flag is on), If not. it ignores the intermpt (and of course fe-enables the
rlln"'l\l.r 'H::'\
_ ............ ~ • .... _ ..".,_ Ifit thin"&:-
••• ~ _ ................
it U'"lC'
""..# th,. ..,.""n'"'''' .... f ,I.. "
....................,.-...... •." w.'" ;... ,,,......_t of
a.&,,~ •• t. • .., .... ,-. ""'''-t.l''''''''.' "..........,..1.. th,.. .... "" ,..,..n, ...." •• .."I.r I." 1-0,..1-...
"L.v. '- , ... v , ......,
keep other NILs on Lhe same temlinal from having to think about it. i guess), and queues a LISP
interrupt for control-C. There is one time when t11is can break down: if the ~ILis suspended
when the AST is delivered. the AST wiJI not be run until the r\1l. is resumed. However. when
the Nil. is resumed. the R:'\Il. delivers ita couple other ASTs which cause the tennina) input and
output flags to be turned on! If this manages to happen before -the control-C AST routine gets
around to checking thesc flags (as it invariably docs). then the SIL will think that this control-C
was for it, and behave accordingly. So, if you resume a NIL and it acts likc you just typed a
control-C, it is probably because of that control-C you typed at the d i sp 1 ay program half an
hour ago; type "n" at the n>Interrupt)'· prompt to make it go away.
There is a design change which eliminates this problem. and additional1y allows controlled
interruptibiHty out of arbitrary wait operations (not just tcnninal input and output, which are
special cased). It involves a sweeping change to lots of code. however. so cannot be put in bits
at a time.
MC:NILMAN;TAJ.K 16
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Ofirjrnttxd't
N II. Manual 295' Peripheral Utilities
28. Peripheral Utilities
This chapter will accumulate documentation on various minor utilities which are distributed
with I'lL. but which are not necessarily part of NIL proper.
28.1 The Predicate Simplifier
Nil offers a predicate simplifier. which simplifies l.lsp-format predicates into disjunctive nonnal
t{lfI11. This progr,lm was originally written hy I )eepak Kapur with thc help of Ramcsh Patil for
th~ PRO'I OSYS 1"'\1 'llItomatic programming project directed h) \Villi4lm Martin at ~v11T in the mid
1lJ70s. Since then. it has heen convened to lise ISH [4]. hrought lip in both liSP \1:\CIII:\F liSP
and '11. and imprm ed at a low levcl. The code for this is not loaded hy dcf~Hl1t in '": it
exists as nil$disk:[nil.utilities]simp. and to load it. the package definition file
nil$disk:[nil.utilities]simp.pkg should he loaded first. This may he perflmned
automatically by use of
( r e qui r e 's imp)
See require. page 123.
This simplifier only really works on simple predicatcs and connectives. It perfonns some
trivial canonicalizations of arithmetic operations and inequalities (equal. greaterp. and lessp), but
it does not truly recognize identities or other relations among them. There is also a read-time
(compile-time) conditionalization for whether it attempts to deal with existential quantification. as
r('nr('c('''tt.,.t
·-r·--- ..··_- h"
......
f"rnlC Ilf th,.. ft,\rnl
J ."'..................- " ..."." ••
(for-some (kl k2 ... kll) pred)
This feature is nonnally turned off, which simplifies the internal dawstructures used and improves
the efficiency in the other cases. Again, simplification of fonns containing existcntial quantification
does not always reduce as well as it should. To get this one would have to recompile simp with
that feature turned on.
simp pred-fonn
Simplifies prcd-fonn. For example.
(simp '(and c d (or a b») =>
(or (and a c d) (and bed»
s1mpor pI p2
s impand pi p2
Approximately equivalent to
(s imp (1 is t and-or-or pI p2»
s 1mpnot pred
Simplifies the not of pred.
simp 0 r 11 s t pred-Iist
S 1mpandl1 s t pred-list
Simplifies the or or and of pred-list.
MC:NILMAN;UTILS 15
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\ Mini-MYCIN
296 N II. Manual
.s 1mpor pi p2
.s 1mpand 1'1 pl
pI and p2 must already be in disjunctive nonna} fonn. i.e .• already simplified (as returned
by some simplification call). l'bisis faster than using simpor or simpand .
• s impor 11 s t pred-list
.$ impandl i st pred-list
Simplifics thc or or and of the predicates in pred-list. which must be already simplified .
• s 1mpnot pred
Simplifies the not of pre(/. which must be ah'c41dy simplificd.
There is also a hack for doing both uniqui1.ing of predic411es returned. and also "atomizing".
associating an atomic symbol with a predicate (which will be expanded out in subsequent
simplification). The fonner was important in the PIW-I0 ~ACI.ISP version when large databases
associating predicates with probabilities were in use. See the source code if either of thesc are
desircd.
28.2 A l\1ini-MYCIN
'Ibis is a small production rule systcm upon which class projects in the MIT course 6.871
were implcmentcd. Some students in the course ulught this tenn by Prof. Peter Szolovits and Dr.
Ramesh PatiJ used this code in NIL. The directory NILSOISK: [MYCIN] has what the students
gut to st

NIL Manual 297 Maclisp Compatihilil) for Macsyma
28.3 1\1aclisp Compatibility for Macsyma
The directory NI L$OISK: [MACSYMA] has some code in that is used for compiling and
running MACSYMA in NIL and that will be useful to anyone porting a MACLISP program.
The file ALOAO. LSP has an autoloading handler that works by handling the :undefinedfunction
error condition. This might be a generally useful thing to have around.
The file PKGMC. LSP illustrates the usc or. pkg-create-package and intern-local in order to
build a namespace that shadows conflicting or incompatibly defined functions and variahles.
The file N I LCOM. LSP gives definitions of the functions map. subst. member. and assoc,
which are compatible with \1 ACI.JSP.
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Foreign Language Interface 298 NIL Manual
29. Foreign Language Interface
29.1 Introduction
It is desireable to be able to can from NIL procedures that are written in other VMS
supported languages. such as FORTRAN, COBOL. PLI. Buss. C. PASCAL. Ian {Basic}. et. a1.. not
to mention procedures written in MACR032. and VMS library routines and system services.
Fortunately this is easy. due to the the uniform VMS object and symhol table file format.
uniform procedure call mechanism. and rich set of 1'\11. datMypes from which to construct
d41tastructures compatible with what various fhreign language routines expect to receive.
The presently implemented interface is by no means the last word in sllch endevors: for
example it makes no allempt to enforce datatype restrictions in argument passing: however. it is
t(lUlH.l to be functional. and is used in the ~II. system ibc1f to access some VMS system services.
to incrementaly debug parl~ of the assembly-language kerna1. and to interface to "numbercrunching"
f'C.·'TRAN subroutines and to some users .existing C libraries.
29.2 Kernel and System-Services
The executable code for such procedures is already in the lisp process address space. therefore
accessing them is only a matter of defining an argument-data-convention interface. searching the
lisp or system symbol table to get the required machine address. and creating a lisp subr
tr'lmpoline. similar to an element of a transfer vectors the VMS linker would create when one
references sharable libraries.
s 1 : defsysca 11 (lisp-name vms-symbol) &rest arguments pees
Does everything needed to reference a routine in "LISP.STU" or "SYS.STBtt. The lispname
is defined as a special-form taking alternating named arguments as in a defstruct
defined constuctor. For example, the routine to convert a vms error code into a humanreadable
string:
(defsyscal1 ($getmsg sys$getmsg)
(msgid :in :long :required)
(msglen :out :word :required)
(bufadr :out :string :required)
(flags :in :byte)
(outadr :in :bits»
(defun decode-vms-error-code {loss-code &optional (flags 15)
&aux len)
(using-resource (string-buffer string Z56)
($getmsg msgid loss-code msglen len
bufadr string flags flags]
N.R. Ca1ls to SI:DEFSYSCALL. and to many other system internal primitives work when
-compiled-, but not when intepreted. The example above is from code in the systems"
internals package.
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NIL Manual 299 V~IS object files
29.3 Vl\1S object files
To caB a procedure in a vms object file the user must do three things. define an argument
interface. call the dynamic loader. and enable the trampolines for specific procedures. For
example:
(def-vrns-call-interface myfoo)
(defun hack-foo ()
(list (hack-vrns-object-file "[gjc.nil]footest")
(enable-vms-call-trampoline
'rnyfoo 'foo "[gjc.nil]footest.stb"»)
(hack-foo)
! Sets up for this BLISS
MODULE FOOT EST =
BEGIN
GLOBAL ROUTINE FQO = 259;
END
ELUOOM
s1:def-vms-call-1nterface name &rest arglisl
Same as defsyscall. but doesn't actually look into any symbol table or create any
trampoline. Only works when compiled.
s1: hack-vms-object-f11e obj-jile
Calls the VMS linker on a single object file. and then reads the executable code into a
bitstring in the lisp address space. Presently a VMS subprocess interface is not
implementcd, (which is the easiest way for lisp to invoke the VMS linker), so instead the
user is asked to execute a VMS command file lisp writes. This happens twice for every
file so hacked. What a kludge.
s1 :enable-vms-call-trampol1ne name vms-symbol slb-jile
Sets up the trampJine for name using the address of the vms-symbol from the stb-file.
29.4 Data Conversion
At a certain level it helps to know the data representations supported by the V AX hardware
itself, and what representations the various language compilers. including lisp, build on this base.
Lets face it, at this point, unless you are willing to deal with such issues its best to forward
specific interface reqllcsts to tile implementors. and wc'll try to at least provide a family of
r
cxisting examples which should make things obvious, or presolved. Even though the macrology
provided by defsyscall et aI. may m,lke it easy. it by no means m,tkes things foolproof. as any
such excursions outside the lisp-world-firewall we set up arc frought with fmstrating debugging
problems.
MC:NILMAN:VMSOBJ 15
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lowcr Ic,"cl routincs 300 NIL Manual
In garhage collection. the system will not be forgiving of any violation of the mles of register
and stack usage. and raw address placement.
29.5 lower level routines
As if the ones above weren"t low-level enough.
s1: locate-symbol-table-value symbol &rest stb-filenames
Returns nu)) or a fixnum.
s 1 : cons truct-sys tem- symbo l-trampo 11 ne hiS-bits lo24-bits
Returns a tr.lInpoline suhr which jumps to the address specified.
MC:NIL~1AN:VMSOBJ 15
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""WWX e m z
Nil. Manual 301 What Will Break
30. What Will Break
Various changes arc anticipated for future releases of NIL, just as some have taken place for
this release. This chapter notes some of the significant implementation changes which have already
occurred. and describes some which are anticipated.
30.1 \Vhat Broke Since Release 0.259
The single 1110S( significant change since release 0.259 is that there arc now four diffcrent
formats of floating-point numhcrs. Bccausc thc new fOl11lalS do not appcar spontancously, and thc
dcfault com"crsion from rational to floating-point still produces double-float. it is unlikely that
this will he particularly noticcable. "About the only possihle point of lossage here is that the valuc
of the system constant pi (page 76) is now a long-float. This is in keeping \vith the philosophy
that such constants should bc in the longest format possible, and that uses which require a shorter
fonnat can usc a form like
(float pi O.OdO)
or
(coerce pi 'double-float)
which will perfonn the coercion at compile time. Most othcr changcs to arithmetic havc been
additions. extensions, and fixes. For instance, the CO~MO~ LISP di\'ision and con\'ersion-tointcger
functions floor, ceiling. truncate. and round now exist. Certain routines (most notably
those four "division" rOlltines. and numerator. denominator. gcd. oddp. evenp. rational. and
i~tiviia:;za) hu;:c ~ccn cxtendcd t,j c\/nipk;.: numh'fs. iii ufJ~i ill dHu\\ Ill'l1lijJlIlaiioll~ 011 gdu~~iall
rationals. See chapter 10. page 71. on numbers. for complcte information.
The usc of nil in a lambda-Jist as a placeholder for an unused var is now discouraged: the
compiler will issue a warning about it. The variable should be named. and then declared with
the ignore declaration, as in
(multi~le-value-bind (foo bar baz) (mumbledy-frotz)
(declare (ignore bar»
... )
A slight change has been made to the loop macro. The syntax
(loop for x in lonnl form2
do ... )
which is interpreted as
(loop for x in (progn fonnl fonn2)
do ... )
is being phased out. except for those "clauses" which are run totally for effect, not for value.
Whcn multiple expressions are encountered in ~ place where a value-returning expression is
expected, a warning is issued, but the expansion is the same as before. The only "clauses" for
which such multiple expressions will remain valid are initially. finally, and do.
There are a numher of other small isolated changes which are not worth listing here, but
should generally be c\'ident when the code is compiled. having to do with what names are
preferred for certain low-level functions, and corrections to what keyworded arguments certain
functions take.
MC:NII.MAN:BREAK 31
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What Broke Since Release 0.259 302 Nil. Manual
Pathname stuff which lIsed to give you SYSSOISK as a device name now (correctly) uses its
tr~inslation (specifically. user-workingdit-pathname). This is mentioned because it was predicted
in the last release.
The length (page 49) and jist-length (page 59) functions have been changed slightly. Neither
finds a non-null termination of the list acceptable any more: this is in keeping with the CO~MON
I.lSP definition. and (for length) is more consistent with its use as a general sequence length
function (a list with a non-null elld is not considered a proper sequence). length continues to
ghe an error if the list is circular: list-length wi1J return nil when given a circular list.
Certain det:llIlts within defstruct (page 125) ha\e changed. as have certain conventions. The
det~IlJl( lype of a defstruct-defined structure is now a typed object: objects of this type can he
checked t(lr wilh typep by lIsing the name of the structure as the type name. The. :conc-name
option is noy,' on by dcf;mlt. and one must specify (:conc-name nil) to get the old behaviour.
Finally. the keywords specified to keywordcd constnlctor macros. and to alterant macros. arc
intended to be keyword symbols (interned in the keyword package). e.g..
(make-person : head /7raJ :name name)
although non-keyword symbols will be accepted in the interim.
Use of "destructuring" with let is bci~g
see nol-Yfl-wrillen.
phased ou.t. Usc the function no/"yel-wrillell instead;
Declaration scoping for special fonns is slightly different than it used to be. It is. in fact.
~nm{'whllt mor(' {'(ln~i~t('nt th;m h('fnr('. (,h~ptl;'r ". which is n{'w. d~St:r!b{'s d('cbra!!0!1S in d('t~i!.
The main difference is that declarations now scope over the "init fonns" in speciaJ forms that
have them. like let. let •. do. prog. ctc. That is. the dc:l-specs in
(let « vo~1 val-I) (vo,-.2 vol-2»
(decl are dcl·spe~l dcl-sper-2 .•. )
Jon11s . •• )
that do not pertain to bindings of the variables va,..] and va,.. 2, are "in force" not only during
the evaluation of jonns. but of "101-] and "101-2. The major consequence of this is that, with
declarations. let cannot be trivially turned into a lambda expression without parsing the
declarations. In the expression
( ( 1 ambda (va,..] va,..2)
(dec 1 are dcl-spec-] dcl-spec-2 ••• )
jonns • .• )
val-1 val-2 )
the declarations have no influence whatsoever on the evaluation of val-] and val-2.
MC:NIL~1AN:BREAK 31
23-DEC-S3

~ •.-..-.......;.....~~-~~~ ~~mlll'''17Iml'I-!ltJ:!.'.rlri!r.iI1I'-'llr II.' .-Tltlr.'.1•••
1717171517_1'.111 _____.-117__.-.t_______
NIL Manual 303 Future Changes
30.2 Future Changes
Some of these are the same as those anticipated as of Release O.
30.2.1 Default Floating-Point Format
The default floating point fonnat is going to change from the current double-float to singlefloat.
This will almost certainly happen with the next release. The format of course could not be
changed with this release and maintain any semhlance of upwards compatihility, because the
I'rcrious release did not support single-float formal. Because of contagion rules. there arc really
just two ways one might start generating single-floats instead of douhle-tloats: when reading.. and
when pertlmning some irrationa1. transcendental. or othepA'ise awful function on rational inputs.
I f in f~lct the change matters at all for an application (it might not if only generic arithmetic was
heing lIsed). then one could avoid problems by judicious lise of explicit cOIHersion to floating
point. and by being careful to explicitly spedt: the exponentiation character in I.lSP source files so
that the datatype will be explicit.
30.2.2 New Pack,lge Facility
The CO\1\10~ LISP package definition is finally final. and should appear in the next release. It
is unlikely that anything other than code which operates on or with packages explicitly will have
to be changed, with the possible exception of references to "internal" in one package made from
another package.
30.2.3 Vector-push and Vector-push-extend
The argument order to vector-push and vector-push-extend will be changed so as not to
be unmnemonically different from that of push. Currently, the vector is the first argument, and
the object to push is the second: these two will be reversed. This change became known just as
release 0.259 became ready, and got lost or forgotten so never made it into this release. Ah well.
30.2.4 l\lultiple Values
In the future, NIL will "natively" support a multiple-value retunl mechanism. For it to do so
requires that the compiler understand them at a moderately low level: it will be producing code
for receipt of them from function calls, it will have to flag function ca11s which will be passing
them back to another caller, and it must recognize and compile away all local multiple-value
passing.
~The
mechanism, which has only been designed at a fairly high level, is this.
Given the compiler behaviour described above. the only place which compiled code can
receive multiple values from is a function can (or a non-lexical throw. but we will ignore this for
the sake of simplicity in this description). This means, that when multiple values arc being passed
back (returned or generated). if we can recognize those function calls which arc simply being
made to pass back any values to their callers (and thus also recognize those which are expecting
MC:N(I.~·1:\N:BRE/\K 31
.~:" ~ . ,', ...
' " ": ,:.~ . ',.~,' .

Future Changes 304 NIL M,mual
some value or values in particular). we can trace up the sL1ck to find the can which is ultimately
expecting the mulliple values. (The function call frames are quite fonnal and stylized in NIL)
So what we do is to have the caner which is expecting multiple values allocate a place for
them on the stack and put a marker there, before it allocates the caU frame for the furiction. it is
about to call.
We have an function calls which simply pass back their values as the value of the function
they are contained in. marked as such. so that examination of the can can detenninc this. In the
following. the calls to foo and bar would be so m~lrked. but baz would not:
(defun frobnic~te (x y)
(if (zerop xl (foo y)
(mvprog! (bar x (sub! y»
(baz (sub! x) y»»
J f (S,lY) within bar there is a call (values Ihis fha/). ulen a special subroutine goes look ing up the
SLICK. finds the frame where bar is called. sees that it passes back its values out of its calling
function. so traces the function frame pointer to the. caller of frobnicate. etc.
If. on the Olher hand. with baz there is a similar values can. tmcing back to Ulat call to
baz reveals that baz is expected to return only one value (of interest. at most), so no further
tracing is done.
There are two further points of interest about this scheme. By appropriate usc of specialized
m:1rkl'rc;: \\lh('r~ !TlllhirJ~ v~lH(,C;: are ('~p('ct('d_ fa~t dispatching may he p('rfiJrm('d for d('?!!ng W!t.~
variolls situations. such as multiple-value-list. for instance.
A somewhat kludgey extension is to use this for things like "number calJingt'-one routine
calling an0ther for (say) flonum value. The one producing the flonum, instead of consing it.
looks back and if the final destination is expccting a Honum in some special way (having, for
instance. pre-allocated a space on the stack for it). then the representation is stored there without
consing. otherwise the value is consed in the heap and passed back via the nonnal value return
mechanism. The kludge involved here is that if the producer is interpreted code, someone has to
coerce the nonnal value return into the hacked onc. This only is necessary when such a compiled
routine is calling into interpreted code, so will probably be done by the interpreter-trapping
subroutine.
The interpreter-trap wrapper must be capable of recognizing when a value has been stored
"properly" into the compiled receiver. because if the producer is compiled and the interpreter has
produced the value such that it got passed back "naturally". then it has been stored already
without being consed, even with intervening interpretation!
It is of note that this stack-searching is not directly analogous to a deep-binding variablebinding
scheme. in terms· of . efficiency and paging overhead etc.~ because in the variable binding
scheme the searching must be done up the entire stack (or alist or whatever) every time. the time
for each search growing in proponion to the depth of the· stack. but for this the search tenninatcs
whenever va1ues are not being passed back to the previous caner.
MC:NILMI\N:BREAK 31
23-DEC-S3

NIL Manual 305 Future Changes
30.2.5 Variable Naming Conventions
CO\1MO!\ LISP is establishing a unifonn naming convention for system-defined parameters and
constants. Essentially. all system-defined parameters (those variables whose values are allowed to
be changed. i.e. that parameterize the behavior of the system) will have asterisks (.) at each end
of their names. Thus. the variable base wiJ] become .base. (~IL uses si:standard-output-radix
now anyway). and package will become .package•.
1\]) system-defined constants. stich as cha~-code-limit. will not. Part of the justification for
tJlis is that the compiler and inlerpreter should he able to determine when one is modifying a
constant. but not a parameter. so th(.~ constants require less visual distinction. This is in fact
curremly the case. as defconstant (page 24) now works.
The change of these variables is indeed going to be catastrophic to both lIsers and the :\11
system itself: Note. however. that one may do (say)
(who-calls 'package :type :value)
to find all modu1cs (i.e.. restricted to compiled code) whicL reference the special value cell of
package.
30.2.6 Garbage Collection-
When the garbage-co])ector is finished. there wiJ] be two major incompatibilities noticeable.
First. tJle format of compiled output files will change. Although initiaHy (for bootstrap and
debugging purposes) old fonnat files will be accepted. it is unlikely tJlat this will still be the case
by the time the garbage collector is released. Even if it is me case that such old files can be
loaded. the garbage-collector will not be able to safely run afterwards. Second. mere is an
incompatible change which must be made to the way unwind - protect is compiled. This cannot
be handled upwards-compatibly. as it involves compiler knowledge about stack usage from tJle NIL
kernel, so old code might not be able to run correctly. Recompilation. of course, will fix
everything.
Obviously. when there is a garbage-conector. dirty operations like playing with addresses and
changing types become substantially more dangerous, and should be avoided by all code except
for the garbage-collector itself.
30.2.7 Error System
A new error system and debugger interface is being designed. The arguments to error,
cerror, and/or ferror may be changed incompatibly. although it is hoped that old uses will be
able to be distinguished from new uses. condition -bind uses will have to be recompiled.
Condition names may work upwards-compatibly, however. Note that now, signal erroneously
forces entry to the debugger if the condition goes unhandled: this will be changed. To enhance
the ability of future code to detect old uses. a few conventions may be helpful:
(I) The first two arguments to cerror should always be t or nil.
(2) Always usc a string for the "error string" or "fonnat string" for all three error functions.
(MACLISP-compatible use of error can get by WitJlout this if the "string" is a symbol, but
contains at least one space in its text.)
MC:NILMAN:BREAK 31
23-DEC-83

Future Changes 306 NIl. Manu4t1
'Inc future debugger, which is mostly· complete now hut needs the new error system. will be
Jnuchbcltcr able to p

·57 '17 . 2'7K2·- 37 r- -iSH'
7
-.
XX
NIL ~-1anLlaI 307 Future Changes
References
1. Steele. G. L.. Common l.isp Refercnce Afanual. Carnegie-Mellon University Department
of Computer Science Spice Project. (in preparation). Actually. it's now in-press with
Digital Press.
2. Steele. G. L.. et al.. An Oveniew of Common LISP, paper prcscnted at 1982 AeM
symposium on LISP and Functional Programming. 1982 ACM 0-89791-082-6/82/008/0098
3. Bawden, A., Burke. G. S .. and Hoffman. C. W.. Alaclisp /:'x/ellsiol1s. MIT I.ahoratory
for Computer Science. Camhridge. Mass. TM-203. July 1981.
4. Burke. G. S .. I.SIl Alanual. TM-~OO. MIT Lahoratory for Computer Science. Cambridge,
Mass .. (.Julle 1981).
5. Burke. G. S. .and Moon. D.. I.oop hef(]lioIlAlacro. TM-169, MIT Laborat 'ry for
Computer Sciencc. Camhridgc. Mas~ .. (Janu~'ry 1981). (Revision in preparation.)
6. Crocker. David H. (rcyised by). Slandard Ihr Ihe Formal of ARPA 11I1('rl1('/ Tex!
Alcssagcs. Network Information Center Request For Comments: SRI Internaltiona1.
~fcnlo Park, CA, (August 1982).
7. Hawkinson. L. 8.. and Burke. G. S. Unfinished, unpublished memo/documen~1tion on
the pretty-printer noted in section 19.5. pagc lR(): cnpicl\ of an int~rim vC'rc;:ion :tr(,
included with ,It distribution kits.
8. Mathlab Group. Alacsyma Reference Alanual. MIT Laboratory for Computer Science,
Cambridgc. Mass., (1977).
9. Moon, D. A., AI AC LISP Reference flrlanual, MIT Laboratory for Computer Science.
Cambridge. Mass., (1974).
10. Postcl, 10n. and Harrensticn. Ken, Time Protocol. Network Infonnation Center Request
For Comments: SRI Intemaltional. Menlo Park, CA. (May 1983).
11. Pratt. Vaughan R.. CGOL - an Alternative External Representation for Lisp users. AI
Working Paper 121. (March 1976)
12. Weinrcb. D., and Moon. D., Lisp Alachille Afanual, MIT Anificial Intelligence
Laboratory, Cambridge, Mass .• (July 1981).
13. White. 1. L.. Constant Timc Interpretation for Shallow-bound variables in the Presence of
Alixed SPECIAVLOCAL Declaralions. paper presented at 1982 ACM symposium on
LISP and Functional Programming. 1982 ACM 0-89791-082-6/82/008/0196
MC:NII.MAN:M;\NUAL 74
23-DEC-83

Concept Index
308
Concept Index
NIL Manual
&aux lambda-list keyword .•••
&kc} lambda-list keyword •••
&optionallambda-list keyword .•
&rest\ lambda-list keyword ••
a-list ••••••
array • • . . • •
31Ta~ disp1:lcemcnt .
arr:1\ mnk .••
:i!'l{'II•••••••
a:-~"ri:iti()n list •••
all\ihar~ \ariahles.
bad:LJlIotc .•.•
bdl:l\ ioural equality
bCllchmarkmg.
bignutn •••.•
bit \cctor ..••
bit-\ cctor-clements loop iteration rath
bib loop iteration path. •
boolean false. •
boolean truth. •
byte specifier. •
byte specifier.
cnaracler nilS •
character code.
character fonl •
character set •
characters loop iteration path •
closures • • . • • • • •
Compilation • • • • • • • •
compiled code module • • • • •
conditionaJizing clause(s}, in loop •
cons dot ••••
cons dot ••••
CRC instruction ••
data type keywords. in loop
decoded time •
denominator • • • • • •
dcstructuring. • • • • •
disembodied propeny list •
dispatch macro character
displaced arrays. • •
displaced index offset. • •
displacing arrays. • • • •
DST _SITE logical name
dynamic extent •
dynamic extent
dynamic scope
efficiency.
clement type •
• • • • • 14
14
13
15
• •••• 63
• )03
103
• 103
qq
b.l
14
• .21h
• 20
.246
• 71
• .7
• 164
• J64
6,28
• •• 6
84
89
• •••• 94
94
94
99
• 164
• •• 13·
• 243
• 243
• 154
• 213
• 214
• 117
• IS7
.234
• •• 4
• .23.26
• 39
• 214
• 107
• • 107
• 103
• 241
12
12
12
.246
• 103. 104
clements loop iteration path
empty Jist ••••
equality •••••••
erTOr conditions. • . •
extcndcd character set •
extent
fCXI'TS
file attribute Jist. .
fhnum ••••.
navurS)SlCm ••
gallssian integer.
gallssian rational
gcncrafilcd \ariablcs. •
~ensyming.
gensym4i ••
hosts •••
identity of objects •
implicit progn •
indefinite extent •
indefinite scope •
, inil file • • • •
integer ••••
internal time ••
interned-symbols loop iteration path .
interpreter closures
iteration. • • • •
keyword symbols •
keyworded arguments • • • • • •
keywords •
kill-ring . • • • • • • • • • • •
lambda list keywords
lambda lists • •
letJist. • • • •
lexical scope. •
lexpr. • • •
lint cell ••••
Ustsyntax •••
logical name. • • • • • •
logical name. DST_SITE. • •
loop ••
macro
macro call •
major modes. •
merging and defaUlting of pathnames • •
meta key •••
mixin flavors
module ••••
163
• .6.28
• •• 20
229
• •• 99
· .• 12
244
205
• •• 71
170
. 5
• •. 5
· .38
.67
• •• 67
197
• •. 20
• •• 22
.12
· .12
287
· . 3
223
• •••• 162
• . • . . .13
144
• •• 6
• • • .14
• •• 6
257
• .13
• •• 13
.26
· .12
244
• •• 70
214
287
241
144
• .23
.23
258
200
• • • • • • 251
175
• 8
23-DEC-83

•• EPS 272
n
n
Nil. Manual
309 Concept Index
multiplc "alucs .••....
multiple accumlilation~. in loop. •
multiple expressIOn . . . . .
name .••
numerator.
obarray. •
object equality
oblist ..••
optimi/ation .
order of c\3Iu:ltion in iteration clauses. in loop.
package. . •
packages . .
pa~sa 11 mode .
patch directof)
patch facility.
patch file . •
patch s~stem definition file .
patchable system. . .
path name defaults. .
penasi\c declaration
plist .•
pname ••
ppss •••
print name
!,rinf n~mp
printed representation.
propeny list •
propeny lists. . • • •
.• 36
152
146
· 6
· 4
121
.20
121
246
147
• 6
121. 127. JJ7
2R9
280
280
280
2RO
280
200
.42
· 6
• 6.66
.89
.66
· (;
· 3
.6.39
39.65
random numbers. .
mnk. array
ratio •.
record ..
scope .•••......•.........
sequences •••.•..•.•.•.•.....
sequential \'s parallel binding and initialization. in loop .
significand . . . • . . • • . . . . • . . •
simple-bit.;.\,ector-elements loop iteration path
simple-string-clements loop ilcralion path . •
simple-\Cclor-clclllcnts loop iteration path
special ....
special variahles
stack vector
streams ....
string . • . .
string-clements loop iteration path
stnlcture •..
~~ n()n~ m stream .
lenll logical name. . . . . . .
tenninatmg the iteration. in loop.
translation table
type specifier •
universal-time.
\atuc equality . . • . . .
\ariahlc bindings, in loop.
vector ••.•
vector-elements loop iteration path
· 86
.103
4
7
12
• 48
.146
• 91
.164
.104
.104
II
• • 11
• 15
.179
• 7
.104
• 7
.18:2
.287
.153
.100
· 16
.234
· 20
.149
· .103
· .163
23-DEC-83
:':.' ~, .~ .. "
,: "." ' - - ,
,

Message Index
310 Nil. M'lnual
Message Index
:ad\'ancc-pos
(to bp) •
. '.
• 277
:pp-anaphor-dispatch. • • • • • • • • • • • • • 177
:dcscribc.
:cqual. •
:cqual
(In \'anill3- namr)
:C\:ll ••••
:c\hibit-sclf .
• • 176
• • 176
• ]77
• • • • • 176
• 176
:pp-anaphor-dispatch
(to vanilla- navor) • •
:pp-dispatch.
:PP" dispatch
(to \'anilla-flamr) •.
:prinl-sclf.
178
177
178
176
:c,hihit-sclf
(to, anilla-fla\or)
:filc-rlis1
:fullcail •
:gct-char
(to bp). • • • • • •
:gct -char-backward
(to bp) •••.•
:gCl-char-forward
(to bp). • • • •
:gct-nandlcr-tor
(to ,'anilla-flavor)
:init ~ with -lcnncap
(to si:display-cursorpos-mixin). • •
:move
(to bp) •
:open ••••
:opcration-handled-p
(to vanilla-navor) •
:oustr
(to si:display-cuTSorpos-mixin) •
:peck -char-backward
(to bp). • • • • • • • • • •
• 178
· .;:06
• 17ft
••••• 277
• •• 277
• •• 277
.177
.211
.277
• 181
.177
• •• 212
• • 277
:prinl-sclf
(to\'anilla-na\'or) •
:raw-oustr
(to si:display"cursorpos-mixin). •
:sclcct-nth
:sclcct-nth
(to vanilJa-navor) • • •
:scnd -if - handl~
(to vanilla-flavor) •
:sct -path name •
:storc-nth •
:5tore-nth
(to vanilla-flavor) •
:sxhash •
:sxhash
(to vanilla-flavor) • • •
:which-operations
(to vanilla-flavor) • •
:wrile-char
(to si:di.~Jay-c:ursorpos-mixin).
:write-raw-char
•
177
212
176
178
177
181
176
178
176
177
177
212
23·DEC·83

NIL Manual 311
Resource Index
si:fab. · .................. . 207
si:nam · .................. . 207
si:rah. · .................. . 207
Resource Index
si:fah ..
si:nam
si:rah. .
si:xah ..
207
207
. 207
••• 208
23-DEC-83

Variable and Const.ant Index 312 NIL Manual
Variable and Constant Index
*
*.
•••
format:*/ # -\'ar.
*:autodin-ii-hash-poiynomial •
*:ccitt-hash-poJynomial . •
*:crc-16-ha,h-polynomial
SIC\c:*&lrgumcnt* .•..•
*hasl'*, , , .•••. , •
lii1lc:"da~ -of-the-week-strings* .
lime: *dd':llIl1- L1nguag.c* • •
time: *default-modc*, . • .
·default-palhIl3mc-dd1ult!\*
stC'\ c:*cuilur-dc\ icc-mode* •
r.,: ·host- inslances*, • . • •
*)u;ld- palhnamc-defaults* .
('ompilcJ:*mL':-..;;ag~-to-tcrminal'! .
·modules* . , • • • . • • • ,
limc:·monlh-strings· . . • . .
compiicr:*opcn-compilc-carcdr-switch
compiler:*upcn -compiic-xref-switch •
·package· . ., •••••
*random-state*, • , • , •
*rcad-dcfault-float-format*•
·scralch-pathnamc-dcfauiLS*
umc:*s),stcm-lImc- kludgc· •
·limclOnc*, •• , ••••
formal: *top-char-printer •
-trace-output·
+ ..
++ .
+++
format:atsign-flag • • • • • •
*:autodin-ii - hash -polynomial •
base
•••••••••
.288
.288
• 288
• • • 191
• • 117
• •• 117
• • • 117
• 274
• • 305
• •• 1.'1
• •• 23()
• • 236
• •• 202
• • 278
• •• 202
• 201
• • 24()
• •. 123
• 237
• 245
• • 245
• • 305
• • 86
4. 72
• • 202
• .241
• •• 238
• • 191
• 179
• • 288
• •• 288
• 288
• • 195
• • 117
• •• 305
double-float-epsilon
Constant •••••
double-float-negative-epsilon
Constant .••
error-output. • •
• .93
• .93
179
format:*/#-\'ar • . 191
fomlat:*top-char-printef. 191
u)mlat:atsig.n- flag.. .
lQ5
fom131:colon-flag. )Q5
1k-hoSl-instances* • 202
internal-lime-units- per-~ond
('onstant. • • • • • •• • • • • . • • • • 223
lcaSl-nCg

NIl. Manual
313 Variahle and Constant Index
most - posit i\"c-Iong - float
Constant ..•....
most - posit ivc-shon - float
Constant. . . . . . .
most-positi\"c-singlc-float
Constant.
msgfilcs.
package.
pi
Constant.
prinlc\ cl
query-io
rcadlahle
~hon - float -epsilon
Constant ...•
short- floal-ncg:ni\c-cpsilon
Constant ..... .
si:chars~ nl:nSm_3Jpha
Constant ....•.
si: charsyntaxSm_both_case
Comitant ..•.•.
si:charsyntax$m_digit
Constant .•.••.
c;i~('h:trc;ynt:n~m~r~!,hir
Cons1.3l1t ..•...
si:charsynt3xSm_lowcr_case
Constant ...•..••
si:charsyntaxSm_standard
Constant. .•.....
si:charsynLaXSm_upper_case
Constant. ••••••.
• 92
.92
• 92
ISO
122.305
.76
17h
179
• 218
.93
.93
102
102
102
101
102
10~
101
si:charsyntax$v_alpha
Constant .•.•..
si:charsynLaX$\'_both_case
Constant •..•
si:charsyntax$,,_digit
Constant ••.•
si:charsyntax$v -.sraphic
Constant •.•••
si:charsyntaxSv_Iowcr_case
Constant ..... .
si:charsyntax$,_standard
Constant ..... .
si:l'harsynt~lx $\ _upper_case
Constant •.
si:dchug -input. . . . . .
si:dchug-output . . . . .
si: lisp-dchuggcr-on -exceptions.
si:loop-usc-systcm -destnlctllring? .
si:standard-output -radix
singlc- flU:ll-Cpsilon
Constant .•....
singJc- float -negali\c-cpsilon
Constam .•
standard-input. • • • .
standard-output . • . .
si:standard-outpul-radix
stcvc:·argumcnt*. • . •
~!~v~: *~di! O!'-dC':ice-medetermina\-io
. • . • . . .
time: *day -of -the-week -strings·
time: ·default -Ianguage* .
timc:*defau1t-modc· .•.
time:*month-slrings*. • •
time:·system -time-kludge-
.102
.102
.102
.101
.102
.102
.101
.180
.180
.21JO
.]59
• •.. 305
. •......... 93
93
· •.. 179
• .179. 195
.305
.274
.278
.179 "
.237
• •• 236
.236
• •.. 237
• .241
23-DEC-83

Function. Macro. and Special Form Index 314
NIL Manual
Function, Macro, and Special ForD1 Index
%char-downcase-code. •
%char-upease-code ••••
%comcn-d_float-to-time
'kom:cn-limc-lo-d_float
%digil-char-in-radix-p
%digil-char-to-weight .
%digit-wcight-to-char •••••••
%dph ..•.•.••.
s~ s:ri·{j\llllm-a.,h -with-o\ crflow-lrapring .
s~:-.:(·:,lhlllllll-dirkrcllrl·-wilh-mcrl1ow-lraJlJling.
s~s:('(/n\lIll1n-JllllS-\\ ilh-mcrllo\\ -tr

NIl. Manual 315 Function. Macro. and Special Form Index
a"h. .83 cdaadr . · 56
a"h& . .89 cdaar · 56
asin .77 cdadar • .56
ao;inh. . 18 cdaddr • .56
aliSOC . • 64 cdadr · 56
aC\sq • 64 cdar • · 56
atan .11 cddaar • · 56
atanh. .18 cddadr • · 56
cddar .56
bigp .19 cdddar • · 56
bil . 109 cddddr. · 56
hil-and . 109 cdddr 5h
hil-andd 109 cddr. · 56
bil-alldc~ . 109 cdr · 56
bit-C · 95
steve:c-u-onlyt 278 char>=. • 95
c .... r . 56 character • .96
caaaar .56 characterp . • 19
caaadr .56 check-argo • 230
caaar • .56 check-type .229
caadar .56 clear-input .183
caaddr • 56 clcar-output • .185
caadr. .56 dose. . .181
caar
· . . • 56 fs:close-all-files • . . .202
cadaar .56 closure. .13
cadadr .56 cJosurep .13.19
cadar. • 56 cJrha~ • .118
caddar • 56 cnarnef • .181
cadddr .56 code-char .96
caddr. · . .56 coerce . 9
cadr • 56 comfile • .245
car • . .56 compile .245
case • 29 coml'ilc-file • .244
~cq. . .30 si:compilc-load-palch. .283
catch • • 35 si:compilc-patch . .283
cdaaar . 56 compiler-let • .245
2J-DEC-8J

Function. Macro. and Special Fonn Index
316
NIL Manual
C'omplex •.•
concatenate. •
cond •.
conjugate
cons •• '. . .
consp ..
si:conslrucl-system-symbol-trampoline
timc:comcn-\ms-timc-to-uni\'crsal-time. •
cop~ -alist
COP}-Iist •••
cop~-scq ••
co('~ -synlhol •
C'OJl~ -tree . .
COp~3IiSt ••.
co('}symhol
cn(')trce.
C(}l\. • •
cosh ••
count ••
count-if.
count-if-not .
crealc-rcadL1ble. •
cursorpos .••
79
50
28
75
57
18
.300
• 240
59
59
51
66
59
59
69
59
77
78
52
52
52
219
• 181.210
time:day-of-the-week •
• ••• 238
time:day-of -the-week-string •
• ••• 237
lime:daylight-savings-p • . •
• .238
timp:n:tylight-c;::winrl;-timf'-!'
· 21~
dehu~ •
.222
deer. ...•
• ••• 39
declare •••
• • .41,243
decode-float. •
• 91
decode-universal-ljme •
· •• 235
si:def-,-ms-calJ-inlcrface ••
• .299
dcfconstant. • • •
• ••• 24
deffiavor ..•••
• • 171.173
define-fonnat-op •
• ••• 194
define-loop-macro
• 157
define-loop-path •
• • 164
definc-loop-sequence-path. •
• •• 163
defmacro .••••••
• • 23
defmethod. • • • • •
• 175
dcfmcthod-primitive ••
• ••• 17S
defparameter. • • . •
• • 24
defstruct. • • • •••
• 125
defstruct - define-type
• .138
si:defsyscall. •
• • 298
defun •
· .22.243
defvar. • • •
• • 24
delete. • ••
• • 53
delete- file • •
.203
delete-if. • .
S3
deletc-if-not •
53
deposit - byte .
90
deposit-field •
86
describe •••
• • 222
si:dctennine-and-sct-tenninal-type • • • • • • • • 211
difference. •
digit -char. •
digil-char-p.
do .•
do· •••
dolist •••
dolimes •.
doveelor
dpb •
dpb&.
ed .•
stC\ e:ed-losc.
stcvc:cd-warn
Slc\'c:cd-warning. .
stc\'c:cditor-hind-kcy .
s1e\c:cditor-dcfun-kcy
eighth • • •
c1a('scd -time. . • • .
ell. . . • . . . . .
si:cnablc-l"ms-caH-lrampoline
ene'ode- universal-time.
si:entcr-rcadtablc.
eq ••
eql ••
equal.
equalp ••
e\'2~-whef! .
even}'
c'-er) •••
exhibit ••
exit -and-run-prOiram
exp
expt •••
tboundp
fceiling • •
moor .••
fifth • • •
file-author
file-crcation -date.
file-length.
filepos • •
fill. • • •
fiU-pointer
find •••
find-if ••
find-if-not
finish-output
si:finish-patch • •
first • • • • • • •
Slc\'e:first-line1. •
fixnunlp • • • ~ • •
fixp •••
float ••.
noat-digit~
float-precision ••
• •• 74
• .97
• ••••.••• 97
· • . . . . .33
· • • . . . • . .33
.33
• .-32
• •• 33
· .85
• •••.•••• 89
24q
• 277
277
278
274
275
.56
223
.4Q
299
235
219
.20
• ••• 20
• 20.176
. ••••• 21
· . 25. 24~
• •• 73
· .55
222
289
.76
.76
• ••• 68
• .81
• •• 81
••••• 56
• 203
203
• •••• 203
203
• ••• 52
106
• •• 51
• .51
· .51
184
283
• ••• 56
• 278
.19
.19
• •• 78
• •• 92
.92
23-DEC-83

NIL Manual
317 Function, Macro. and Special Fonn Index
float-radix.
float-sign
floatp ..
flonump.
floor ..
fmakunbound .
force-output.
format ..•.
fonnat -eharpos.
(omlat- flale. .
fon11:I1- form feed •
form:1l- fresh -line. .
fOrm:lI-lcprinc .
fonnm-lincl .
fo01131- prin 1. .
funn:1t-pnne.
formal-Iah-to
formal-Icrpri. . .
fom1al-tyo .
formal-) -or-n-p.
fomlat -ycs-or-no-p
fourth . • .
fquery ..
fresh-line.
fround ••
fs:close-all- files
(c;:process- in -load-environment. •
f~C' •..
«.ct...•
("ymc\,al
ftruncate
funcall .
gcd .••
gcnsym •
gcntcmp.
get •••
get - a-byte.
get-a-byte-2c ••
si:gct-call-meters. • •
get-decoded-time.
get-internai-rcai-time.
get-intcrnai-run-time •
gct-output-strcam-string. • •
gct-pnarne. • •
set-privileges • • • •
get-properties • • • •
si:get -system-version •
si:get -system -version -list
·gct-universal-time
getf •••••
gethash •••••
si:gctjpi-string • •
si:getjpi-value •
gcll. • • • ••
si:gctsyi-string .
si:getsyi-value •
.91 globali7.e ...
.92 go •.•••.
.19 graphic-char-p
• 19 grcatcrp .••
.79
.68
184
187
196
196
196
1%
1%
196
195
195
196
196
195
197
197
.56
}97
185
.81
202
206
.Ql
.69
.69
. 81
.30
. 75
.67
.67
.65
III
111
•• 225
235
• 223
• 223
182
.69
233
.40
282
•••••• 282
•••••••• 235
.39
US
242
241
.69
242
242
si:hack-vms-ohjcct~file. .
haipart .•..•
hash -table-count
hauiong ....
haulong& ...•
host-software-typc .
if ...
imagpan
illcf ..
init- file-pathnamc .
si:initiali/c-patch-s},stcm
int-char ....•
intcger-decode- floal
inlet! ," r-)ength .
intcrr ...
intern-soft
intersection •
isqn .•
last •
stc\'c:last-linc? .
timp"I:llO:t .IO:llnn::ly-in-:l!"ril
timc:last-sunday-in-uctoher .
tcm .
Idb •••
ldb& ••
Idh-tcst
IdiIT •••
time:lcap-year-p. •
length
lessp.
let •••
let· •
lexpr-funcall
lexpr-send • •
lexpr-scnd - forward.
stcve:line-next. • •
steve:line-previous •
lisp-implementation-type •
lisp-implementation-version •
list • • •
list· • • •
list -length
listen
listp. • •
load .••
load-byte.
load -patches
si:locale-symboi-tab)c-valuc •
log ••
logand ••••••••.•••
.122
• 34
· 94
· 74
.299
· 84
.118
· 84
• 89
.232
• 2R
5
· 39
.200
.284
.96
· 92
· 83
.122
.122
• 62
.77
· 58
.278
.'~Q
.239
· 75
• 85
· 89
· 85
.60
.238
· 49
• 74
• 26
• 26
• 31
.172
.173
.276
.276
.232
.232
• 57
• 57
· 59
.183
• 18
.204
.90
.281
.300
.76
· 81
23-DEC-83

Function. Macro. (Iud Special Fonn Index
J18
Nil. Manual
logand& .•.
Jogandcl ••
. Jogandc 1 &. .
logandc2 •••
Jogandc2& ••
Joghitp •
logbitp&.
logcounl.
logcount&
logcqv ••
Jugcq\& •
Jo~ior .•
Jogior& •
lognand •
Jognand&
Jugnm .•
Jognor& •
lognnt. .
lognot& •
logon". ..••.
logorcl& •••
lugurc2 .
logorc2&.
logtest ••
loglcst& •
logxor. • • •
logxor& •
lonr-c.;itl'-n:unl'
si:lnokup-rcadlablc
1001' • • • • • •
loop-finish. • • •
si:lool'-gcntemp. .
si: 1001'-namcd - ,'ariable.
si:loop-ta~soc. •
si:loop-tequal. •
. si:loop-tmcmber
lower-case-p .•
machine-instance.
machine-type •
macro .••••
make-array. • .
make-bit-vector
steve:make-bp •
make-char •••
si:make-fab •••
make-hash-table •
makc-instance ••
stc\'c:make-line. •
make-list ••
si:make-nam. • •
si:makc-rnb • .
make-random-state • •
l'Otc"c:makc-scrcen-im3ge •
maL:e-sequence. • • • •
makc-string • • • • • •
maL:e-Slring-inpul-Slrcam
88
82
88
82
88
81
89
83
89
81
88
• • • • • 81
RR
82
88
82
88
83
89
8~
88
82
88
83
89
81
88
· :n,
• 218
• 144
• 153
• 166
· 166
.1b6
• 166
• 166
• 9S
• 232
• 232
• 24
• 103
• • 110
• ••• 275
.96
• 207
• ••• 118
• • 171.173
• 276
• 58
• '2D7
• • 201
• 86
· 279
.50
• • 114
.182
makc-string -output-stream.
makc-~)mhol • • • •
makc-sy nonym -stream
make~vcctor. •
si:make-xab •
makunbound.
map .•.
mapaUfilcs.
mapatoms.
mapc .••
mapcan •
mapcar •.
mapcon ..
mapl •••
maplist· •
mask-field
n13X
•••
mad ....
max& •
. mcmber ••
memq • • • ••••
mcrgc-pathnamc-dcfauits
min.
minS ••
min& .•
minus
minu~ ••
m~ ...
timc:modc-languagc- fClch •
si:modulc-sourcc- file .
time: month -length
timc:month-string • • • • •
timc:moonphase • • • • • •
multiple-value. • •
multiple-value-bind
multiple-value-list .
multipie-value-prog1
multiple-value-setq •
steve:mx-prompter •
name-char
namestring
nbutlast ••
ncone. • •
noons •••
si:new-palCh-system
nibble •••••
nibble-2c ••
nintersection •
ninth. • • • •
not •••••
stcve:not -buffer-begin
!neve:nol-buffer-end
stcve:not-first-line •
stcve: not -last-line • • • •
notany ••••••
notc-modute-pathname • •
182
.b6
182
108
207
• •. 68
32.54
204
122
· . .31
• •• JI
• •• 31
. .31
• • • -' 1
.31
• •. 85
.74
• •• 91
• •• 87
.61
.61
201
.74
.91
.87
.75
.73
• •• !H
2~n
221
238
237
238
• •• 37
• • .37
•• 37
.37
.37
279
• •• 97
199
.59
.58
• •• 57
284
• • 111
111
• •• 62
.56
• •• 28
278
278
278
278
• •• S5
124
23-DEC-83

NIL Manual
319 FunClion. Macro. and Special Form Index
si:nntc-primitivc-font .
notc\ct).
nrcconc.
nrc\"crsc.
nscl-di/Tcrcnce.
n~t -cxclusi,"c-or .
n~ring-down~c ..•
nstring-upcasc • •
nsublis •••
nsubst ...
nsubstitute. .
nsubstitute-if
osubslillltc-if -not.
nth .•.•...
SIC\ c:nth-ncxl-Iine
stc\c:nlh-prc\ inus-line
nthcdr .
null ••
numbcrp
mmion
oddp .•
opcn ••
or •••
ouslr •
stc"c:overwrile-done
ste\c:merwrilc-homc •
~1(,\(,:O\'f'rwrir('-~~rt "
SIC\c:o\,crwrilc-tcrpri .
si:paclcage-symbolconc.
si:pag~faull-count.
pairlis ..•
pairp ••••••
pathname ••••
pathnamc-device •
pathname-directory •
pathname-host •
pathname-name • •
pathname-type. •
pathname-version.
peck-char ••.••
pkg-create-package •
pkg - find -package.
pkg-goto
plist ••
plus ••
pJusp ••
stcve:point. •
stcve:point-selected. •
pop ..•.
position •••••
position - if. . • .
posilion-if-nol. •
utils:pp-inlo-file •
prctty-prin 1 . • •
prcny-prinl-datum. •
WI
· .55
.58
.52
.62
.62
115
115
· .61
.60
. 54
.54
• •• 54
.57
· . 276
· 276
.57
• 18
.19
.62
.73
180. 211
.29
• . 185
• • 279
• 279
27Q
279
.70
• 224
• •• 64
.19
• • 199
· 199
199
• 199
••• 199
199
• • 199
••• 183
• • 122
. ...... . 122
122
.69
.74
.73
276
••• 276
••••••••• 38
.51
.51
. 51
228
186
187
prclty-print •
prclly-print-datum.
print
prine. . • • . • • .
print •.••...
limc:print -bricf-universal-timc. •
lime:print-current-datc. . • . .
limc:prinl-current-mail-fonnat -date
time:print-current-moonphase
time:print-currcnl-time •
timc:prinl-datc • .
si:print-hcrald. . •..
utils:prillt - into-file. . .
timc:prim-moonphasc
f1rinl-s~ stcm - hisIOt)" . .
print - s~ stcm -modi ficalions
tiflle:print-lime • • • • • .
timc:print-uni\crsal-datc .
timc:print -univcrsal-mail- format-dale. .
timc:print -uni\crsal-lime
probc-file . . • • . • . . . .
proceed-nil. . . • • . • . • .
tkproccss-in-Ioad-cnvironmenl
proclaim •••••
prog .
prog*
progl
nroo') r· -4,;'-
progn
prog"
progw
progwf ••
pmgwq.
provide.
psetq
push.
putprop
quit •••
quotient •
random ••
rassoc ••
rassq •••
rational.
rationalize
si:re-edit -palch
read •••••
stevc:rcad-buffer-name •
read-byte •••••
read-char •••••••
5tc\'e:rcad-file-name
rcadline • • • • • • •
steve:rcal-arg-sup? •
rcalpal1 .•••••
.187
.un
.185
.185
.185
.236
.236
.236
.239
.235
.236
.282
.228
.239
· .281
.281
.235
.2''''
.2~, ,
.235
.203
.llN
.206
46.243
· . 35
35
22
:22
22
27
• . 27
27
· 27
.123
· 26
38
· 65
.289
75
. ••. 86
· .64
. ••• 64
• 78
. ••••• 78
• .283
.184
.279
.184
· .183
.279
.184
• .278
· • 5
.239
tirne:rcgular-amcrican-daylight-saving.s-time-p .
rem •••••••••••••.••••• ". 80

Function. Macro. and Special Fonnlndex
320
Nil. Manuell
remaindcr
remf •.
rcmhash ••
remmc ••.
rcmo\c-if ••
remmc-if -nOl
rcmpTop ••
rename- filc
rcplacc •••
require •.
si: r~q uirc-charartcr
l'i: rcquin:-l'haracter-Jhnum •
rl'!\~l- fi 11- poi III er
rest ••.••
return .•••
returll-from
rC\3ppcnd .
rC\'crsc . • •
si: mlsSclose
si:nns~n)\)ncct
si:rmsScrcate .
si:nnsSddc(c .
si:nns$disconncct .
si:rmsSdisplay. •
si:rmsSenter • •
si:rms$crase •
si:rmsScxlcnd.
si:rms$find. .
si:nnsSnush
si:rmsSfrcc. •
si:rms$g~t • •
si:mlsSnxt\'ol. • • • • •
si: mls$opcn
~i:rmsSparsc •
si:nns$put •
si:nnsSrcad.
si:rms$reJcase. •
si :nnsSrcmove
si: nnsSrename
si: rmsSrcwind.
si:rms$scarch •
si:rmsSsctddir.
si:nns$space . • • • • •
si:rmsStrunc •
si: rms$update.
si:nns$wait.
si:nns$write • • • • • •
room •
rotalef.
round.
rpJaca •
rplacd •
runtime •••
sarncpnamcp •
SlC\'C:savc-alJ - files.
sbit. • • • • • •
• • 80
• • 40
• 118
53
53
53
65
• 203
52
123
• • • • • 97
97
• • lOb
57
• • • • • 34
34
S8
52
• 208
· • 20R
.208
• 208
• 208
• 208
.209
• 208
• 208
· ?OR
• 208
• 208
.208
.208
• • 20R
.209
.208
• 209
.208
.209
.209
.208
• .209
• 209
.209
• 209
.209
• 209
• 209
.234
39
79
56
••••• 56
.223
.66
• 277
• 109
scalc- n03t •
schar •••
second ••
stcvc:scJcct -I'oint .
!.1c"c:sclcct-point-in-currcnt-window
seiCt1q . • • • • ••••
send ••••
send-forward
set •••••
set-di ffcrcnce
set-cxclusivc-or •
sel-ldb& .•••
si:~t -~nch-cO\·irollmcnl. .
set -I'rhilcgcs . • • • . • • • • • .
si:sct-!\ystcm-st:nus. •
sct-tcmlinal-typc.
self •.
setl'list • •
selq .•
~tsynlax .•••.
lICtsyntax -sharp-macro. •
~c\"c:sctul'-modc-arca
seventh ..
5gner .•••••
shillf. • • • • •
short-site-name
si:show-call-mclcrs. •
Q:lJ.jr1 .
si:%syi ••••••
si:abon-p3Ich . • • •
si:add-cscape-char-syntax •
si:add -list-syntax. • • •
si:add-numhcr-syntax ••
si:add-packagc-!o"yntax •
si:add-patch. • • • • •
si:add-prcfix-op-macro •
si:apTopos-@cnerate. • • • • • • •
si:compilc-load-patch. • •
si:compile-patch • • • • •
si:construct-syslcm-symbol-trampoline. •
si:def-vms-call-intcrface. • • • • •
.91
114
.56
276
276
.30
172
172
.• 69
...•••. 62
. •.••..• 62
•.• 89
28]
233
283
211
.38
.69
.25
si:dcfsyscaU • • • • • • • • • • • • • • • •
si:dctcrmine-and -set-tenninal-type •
si:enablc-vms-call -trampoline
si:enter-readtable. • •
si:finish-palch • • •
si:gct-ca11-meters ••••
si:get-system-version • •
si:gct -syslem-version-list
si:gctjpi-string •
si:gctjpi-value • • • • • • •
si:gctsyi-string. •
si:gcL~yi-value .•
si:had-vms-objcct-fiJc •
si:initiaIi7c-patch-systcm •
si:locate-S}mbol-tablc-value •
si:lookup-rcadtable. • • • •
~IR
218
279
.56
109
••• 39
232
225
242
242
283
219
219
219
219
283
219
221
283
283
300
299
298
211
299
219
283
225
282
282
242
241
242
242
299
2.84
300
218
23-DEC-83

NIL Manual
321 Function, Macro, and Special Form Index
si:loor-genlemp ...
si: lool'-n;ullcd-\'ariablc
si:loop-tassoc •
si:loor-tequal •
si:loop-uncmbcr .
si:make- fab . .
si:makc-nam.
si:make-rab .
si:make-xab. .
si:modulc·sourcc-file
si:ncw-palch-s),slcm
si:uolc-rrimili\ c- fOIll .
si:r:1ckagc-!'~ mholconc.
....
si:ragcl~lUlt-rount.
si:rrinr-t.crald . . .
si:rc-cdil-r:1lch ..
si:rcqllirc-charactcr . .
si:rcquirc-characlcr-{hnuIn.
si:mlsSciosc . .
si:nllsSconncct .
si:nnsScreatc. •
si:nnsSdcJctc.
si:rmsSdisconncct .
si:rrn~Sdisplay .
si:nnsScnter. •
si:rmsSerasc •
si:rmsScx tend
c;i'rmc;~finn
si:mlsSflush
si:mlsSfrcc.
si: mls$get .
si:rrnsSnxt\'ol. .
si: nnsSopcn . •
si: rmsSparse •
si:nnsSput. • •
si:nns$rcad . .
si:nnsSrelease • • • • •
si:rmsSremove •
si:rmsSrename •
si:nnsSrewind
si:rmsSscarch. •
si:rmsSsetddir
si: rmsSspace. •
si:rmsStrunc. •
si: rms$update
si:rms$wait • •
si:rmsSwJite •
si:sel-patch-environmcnl.
si:sct-systcm-status. .
si:show-call-mcters. •
si:subtract -call-meters .
si:systcm-vemon-info.
si:trnlog. • • • • • •
si:updatc-systcm -statuses?
signal ••
signum.
signum&
]66
16b
166
166
166
207
207
207
· 207
221
284
101
.70
224
282
· 283
.97
. 97
208
208
208
208
208
· • 208
209
208
208
2(\8
208
... 208
208
• . 208
208
209
••• 208
• • 209
208
209
· 209
208
209
209
209
• • 209
209
209
209
283
283
225
225
282
209
282
229
.77
.88
simp.
simpand ••
simpandlist
simplc-hit-vector-Icngth
simple-general - vcctor-Iength
simplc-vector-Iength
simpnot ..
simpor .•
simporlist.
sin
sinh.
sixth.
somc.
son .
sonC3r .
utils:source- need -COnlrilc?
sqrt •••
s..\tatus ..... .
stablc"son ~ . . •
st:mdard-char-p .
status ••••
Sle\c:argumcnt? • •
slc\'c:huffcr. . • •
slcYc:buffcr-begin? •
stcvc:huffcr-cnd? • • • . •
stevc:c-u-only? • .
stcvc:cd-Iosc ..
stc\c:ed-waming.. .
Slc\c:cditor-bind-kcy.
stc\,c:edilor-dcfun-key •
stevc: first -line?
slc\c:lasl-linc? ••
stcvc:linc-ncxt. • •
steve:Jine-previous .
steve:makc-bp. . • .
stevc:make-line • • •
steve:makc-scrcen -image
ste"c:mx" prompter. •
stc\'c:not-buffer-begin
steve: not -buffer-end •
steve: not - first -line •
stcve:not-last-line ••
Sleve:nth-next-line. •
stevc:nth-previous-line •
stevc:overwritc-done.
steve:overwJite-home •
stcvc:overwnte-start •
stevc:overwritc-tcrpJi. •
steve:point • • • • •
Slevc:point -selectcd. •
stc"e:rcad-huffcr-name •
stevc:rcad-file-name
stcvc:rcal-arg-sup? •
stcvc:sa,c-all-filt.'S •
stcvc:sclcct-point. •
stcve:sclcct-point-in-currcnt-window
.295
.295
.295
· .110
.109
.109
.295
.295
· .295
77
• 78
50
54
55
55
.127
76
87
55
94
87.224
.278
.276
.278
.278
.278
.277
.~T?
.278
.274
.275
.278
.278
.276
.276
.275
.276
.279
.279
• .278
.278
.278
. .•. 278
.276
.276
.279
.279
.279
.279
.276
.276
.279
.279
.278
• •• 277
.276
.276
23-DEC-83

Function, Macro. and Special Fonn Index
322 NIL Manual
stc"e:sctup-modc-arca. •
Slc\c:with-no-passali
streamJl. • .
siring . . . .
string-apJlend
slring-char-p.
siring-downca!>c.
siring-equal • • •
!.lring-equal-hash .
string-greate", . .
siring-left-trim ..
siring-kngth .. .
slring-lcssl1 ... .
sliing-lIol-(.'qual
siring-JHlI-grcatcrp
stnng-nol-Icssp. •
Slring-nre\ers~ . •
slrillg-re\ erse. . .
slli IIg - re\ crsc-sea rch . .
string - n?\ l'rsc-Sl':Jrch-char
st ring -rc\crsc-scarch" not -char
slring-rc\crsc-scarch-not-SCI •
slJing-re\'crsc-search-set .•
st ring - right - trim •
string-search. • • ••
string-!iCarch-char. • • • • • • • •
string-scarch-nol-char.
!ilring-'I('arrh"nnr-~t
string-search-sct
siring-Irim. •
!lolring"upC3:ie •
string/: .
siring( .•
Slring = •
Slringp
subl •
sublis. •
subseq.
subsctp
subst •
substitute
substitute-if •
substitute-if - not
substring. • • •• •• • • • •
si:suhlract-call-meters • •
subtypep.
svref ••••••
sxhash ••..••
sys:sxhash-combine •
symbol- function
S} mbol-Jlame • • •
!\ymhol-paciage.
symbol-pliSl ••
• • 279
• • 278
• 179
• • 112
• 115
• • }9
• •• JJ4
• • • • 113
• • 119
•.•• 113
• 115
• 114
•••• 113
• •• 113
• 113
· .• ID
• • • • • 115
• • • • • 115
)]6
• • • • 116
• 116
• • 116
••• 116
• US
• 116
• • 116
• • 116
111\
• • • J 16
• 115
• 114
• • 113
• 113
• 113
• 113
• • 119
• • 114
• 113
19
75
• • • • • 60
••••• SO
62
60
53
• • • • • 54
54
• 115
.225
• 18
• 109
• 119
• • 119
68
66
• • • • • 67
6S
symhol - \'aluc
symholconc •
symbolp ••
symcvaJ .••
!l)'s:%fixnum-ash-with-m·crflow-trapping.
!\ys:%fixnum- differencc-with -overflow-lraJlJling • .
sys:%fix num -plus-with-overflow-trapping .
sys;%fixnum-limcs-with-ovcrflow-trapping •
s),s:sxhash-combinc •••
· .68
· .70
• • 18
.69
.90 .
· .90
· .90
• .90
119
si:syslcm-vcrsion-info. • 282
taghod) .
tailp •
lan ••
tanh.
tenUl •
tcrpri •
thc ••
third.
Jhrow.
time.
. ....... .
.......
timc:comcn-\·ms-Lime-to-uni\crsal-timc.
limc:da)-of-the-wcck. • • • • •
timc:day"of-the-wcci-string.
timc:daylight-savings-p • • •
time: daylight -salings-time-p •
time: last -sunday-in-april • •
'imp'I~~f-Qlnrt~y-in-n("tn~r
timc:lcap·ycar-p. • • • • •
limc:modc-languagc-fctch •
timc:month -length
timc:monLh-string • • • • •
limc:moonJ'hasc . • • • • •
time:prim-bricf-univcrsal-time • •
time:print-current-date • • • •
timc:print -current-mail-fonnat.. date.
time:print -currenr-moonphase
time:print-current-time •
time:print - date. • • •
timc:prinl-moonphase ••
• •• 34
• .5Q
••••••• 77
•••••• 78
• •• 56
185
.47
• •• 56
• •• 30
223
• 240
238
237
238
238
239
~3Q
. 238
237
238
. 237
238
••••• 236
236
•• 236
239
235
236
239
timc:print-time. • • • • . . . . . . 23S
time: pri nt ·universal-date ••••• 236
time:print-univcrsal-maiJ-(onnat-dale. •
236
time:print-universal-time • • • • • • •
235
timc:rcgular-american - da)·Jjg.ht -savings-time-p • 239
time:timezone-string • • • • •
238
time:verify-date
238
time:zoneconv •
• • • • • 239
timer. • • • ••
223
times. • • • •
. . ~ .75
time:timezone-suing
238
to-SIring •
112
trace •••
179,220
si:tmlog ••
209
truncate ••
• •• 79
typcca.~ ••
• •• 30
typep. •
.18

N II. Manual
323 Fum:tion. Macro. and Special F0n11 Index
union.
unless.
unread-char.
unwind-protcct.
si:updatc-systcm -statuscs? .
uppcr-case-p . . • • .
uscr-homcdir-palhnamc .
uscr-scr3tchdir-pathnamc
lIscr-workingdir-palhnamc .
1I1ils:pp-into-lilc. • . . .
1I1ils:print-illI0-lilc .•..
1IIils:sourcl'-nl'cd-compilc? .
utils:\a~-sourrc-lilc ..•.
utib.:\a~-s()urcc-nccds-rccompilc? .
\alrel .. .
vailies .. .
\alucs-list.
\'alucs-\ ector.
ulils:vas-sourcc-Iilc .
utils:\:ls-sollrcc-nccds-rccompilc? .
\CClor •••••
vcctor-lcngth
vcctor-pop . •
vcctor-push .
vcctor-push-extend •
\,C'rforp ....
\cri(v. . . . • .
timc:\crify-datc
vref ••
.62
.29
184
.36
282
.95
199
• 200
200
228
228
• 227
227
227
289
.36
.37
.37
227
227
· 109
108
106
106
106
lQ
228
· 2J8
108
when •.
whercis •
who-calls.
with-input - from -string
stcl'c:with-no-passaU •
with-oJ;>en-file. • . •
with-output-to-string •
writc-bits. •
write-byte. .
write-char.
write-line.
write-string •
loons •••
y-or-n-p ••
yes-or-no-p. .
zerop. • • ••
time:loneconv • •
\&.
.28
221
221
182
• 278
181
182,
186
•••••••• 186
185
· 185
185
.57
197
• • 197
.73
239
.88
.91
87.88
23-DEC-83